Writing Extensible Code Using Event Dispatcher

Demonstrate refactoring a typical Controller to using Symfony2 EventDispatcher component to make writing decoupled code easier.

Transcript

1. WRITING EXTENSIBLE CODE
   USING EVENT DISPATCHER
   John Kary
   Kansas City PHP User Group, October 2012
   

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2. ABOUT
   PHP since 2005
   Contract PHP Developer in Lawrence
   Education & Trucking Industry
   Previously of University of Kansas - IT
   

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3. EventDispatcher
   http://bit.ly/sf2-event-dispatcher
   {
   "require": {
   "symfony/event-dispatcher": "dev-master"
   }
   }
   php composer.phar update
   

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4. Overview
   1. Procedural PHP
   2. Refactor to Object-Oriented PHP
   3. Extensibility
   4. Controllers in Model View Controller
   5. EventDispatcher concept
   6. Refactor to using an EventDispatcher
   7. EventDispatcher caveats
   

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5. Maybe you know about...
   JavaScript Events
   Basics of Object-Oriented
   Programming
   Inheritance
   Polymorphism
   Encapsulation
   Abstraction
   Delegation
   Dependency Injection
   Single Responsibility Principle
   Separation of Concerns
   MVC
   

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7. DemCrookidWigitz.com
   

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8. John,
   Customers are unhappy. Send
   them a “Welcome!” email after
   they register on the web site.
   Tell them we are glad to have
   them as a customer.
   That’ll teach ‘em. Do it now.
   The Boss
   The Boss
   

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9. 0Before We Begin
   

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10. 0Before We Begin
    UTION CAUTION CAUTION CAUTIO
    

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11. The Code
    In This Presentation
    Is Not
    Production-Ready
    

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12. 1Procedural PHP
    

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13. Procedural PHP
    $_POST = array(
    'name' => 'John Kary',
    'email' => 'john@johnkary.net',
    );
    $to = $_POST['email'];
    $subject = 'New Account';
    $message = "Welcome " . $_POST['name'] . "!
    Your new space has been created! Use this link to login:
    https://activate.demcrookidwidgitz.com/code/Sq9284tWBnWgpjw
    Thanks!
    DemCrookidWigitz";
    $headers = array();
    $headers[] = 'From: accounts@demcrookidwigitz.com';
    $headers[] = 'Reply-To: contact@demcrookidwigitz.com';
    $headers[] = 'X-Mailer: PHP/' . phpversion();
    mail($to, $subject, $message, implode($headers, "\r\n"));
    

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14. 2
    Object-Oriented PHP
    

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15. Object-Oriented PHP
    $_POST = array(
    'name' => 'John Kary',
    'email' => 'john@johnkary.net',
    );
    $to = $_POST['email'];
    $subject = 'New Account';
    $message = "Welcome " . $_POST['name'] . "!
    Your new space has been created! Use this link to login:
    https://activate.demcrookidwidgitz.com/code/Sq9284tWBnWgpjw
    Thanks!
    DemCrookidWigitz";
    $headers = array();
    $headers[] = 'From: accounts@demcrookidwigitz.com';
    $headers[] = 'Reply-To: contact@demcrookidwigitz.com';
    $headers[] = 'X-Mailer: PHP/' . phpversion();
    mail($to, $subject, $message, implode($headers, "\r\n"));
    Customer
    

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16. Object-Oriented PHP
    class Customer
    {
    public function __construct(array $data)
    {
    $this->name = $data['name'];
    $this->email = $data['email'];
    }
    public function getName() {
    return $this->name;
    }
    public function getEmail() {
    return $this->email;
    }
    }
    

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17. Object-Oriented PHP
    $_POST = array(
    'name' => 'John Kary',
    'email' => 'john@johnkary.net',
    );
    $to = $_POST['email'];
    $subject = 'New Account';
    $message = "Welcome " . $_POST['name'] . "!
    Your new space has been created! Use this link to login:
    https://activate.demcrookidwidgitz.com/code/Sq9284tWBnWgpjw
    Thanks!
    DemCrookidWigitz";
    $headers = array();
    $headers[] = 'From: accounts@demcrookidwigitz.com';
    $headers[] = 'Reply-To: contact@demcrookidwigitz.com';
    $headers[] = 'X-Mailer: PHP/' . phpversion();
    mail($to, $subject, $message, implode($headers, "\r\n"));
    Customer
    WelcomeEmail
    

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18. class WelcomeEmail
    {
    public function send($to, $name) {
    return mail($to, $this->getSubject(), $this->getMessage($name), $this->getHeaders());
    }
    protected function getSubject() {
    return 'New Account';
    }
    protected function getMessage($name) {
    return "Welcome " . $name . "!
    Your new space has been created! Use this link to login:
    https://activate.demcrookidwigitz.com/code/Sq9284tWBnWgpjw
    Thanks!
    DemCrookidWigitz";
    }
    protected function getHeaders() {
    $headers = array();
    $headers[] = 'From: accounts@demcrookidwigitz.com';
    $headers[] = 'Reply-To: help@demcrookidwigitz.com';
    $headers[] = 'X-Mailer: PHP/' . phpversion();
    return implode($headers, "\r\n");
    }
    }
    

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19. Object-Oriented PHP
    $_POST = array(
    'name' => 'John Kary',
    'email' => 'john@johnkary.net',
    );
    $to = $_POST['email'];
    $subject = 'New Account';
    $message = "Welcome " . $_POST['name'] . "!
    Your new space has been created! Use this link to login:
    https://activate.demcrookidwidgitz.com/code/Sq9284tWBnWgpjw
    Thanks!
    DemCrookidWigitz";
    $headers = array();
    $headers[] = 'From: accounts@demcrookidwigitz.com';
    $headers[] = 'Reply-To: contact@demcrookidwigitz.com';
    $headers[] = 'X-Mailer: PHP/' . phpversion();
    mail($to, $subject, $message, implode($headers, "\r\n"));
    Customer
    WelcomeEmail
    Controller
    

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20. class Controller
    {
    // POST http://demcrookidwigitz.com/person
    public function newCustomer() {
    $customer = new Customer($_POST);
    $email = new WelcomeEmail();
    $email->send($customer->getEmail(), $customer->getName());
    }
    }
    Object-Oriented PHP
    

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21. John,
    Advertising wants to know
    how many new customers
    we’re getting. Setup some
    logging. I don’t want their
    grubby hands on the database.
    That’ll teach ‘em. Do it now.
    The Boss
    The Boss
    

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22. 3Disk Logging
    

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23. Disk Logging
    class Controller
    {
    public function newCustomer() {
    $customer = new Customer($_POST);
    $email = new WelcomeEmail();
    $email->send($customer->getEmail());
    $dLog = new DiskLogger('/logs/prod.log');
    $msg = 'Sent welcome email to '.$customer->getName().
    ' at '.$customer->getEmail();
    $dLog->log($msg);
    }
    }
    

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25. John,
    Marketing wants to run
    statistics on orders. Keep
    them away from the database
    too. Just add to that other log
    file we setup for Advertising.
    That’ll teach ‘em. Do it now.
    The Boss
    The Boss
    

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26. 4More Disk Logging
    

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27. More Disk Logging
    class Controller
    {
    public function newCustomer() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $msg = 'Sent welcome email to '.$customer->getName().
    ' at '.$customer->getEmail();
    $dLog->log($msg);
    }
    public function createOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Created order ' . $number);
    }
    public function cancelOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Cancelled order number ' . $number);
    }
    }
    

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29. 5Moar Logging!
    

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30. class Controller
    {
    public function newCustomer() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $msg = 'Sent welcome email to '.$customer->getName().
    ' at '.$customer->getEmail();
    $dLog->log($msg);
    $eLog = new EmailLogger('boss@demcrookidwigitz.com');
    $eLog->log($customer->getName() . ' has registered!');
    }
    public function createOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Created order ' . $number);
    }
    public function cancelOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Cancelled order number ' . $number);
    $eLog = new EmailLogger('boss@demcrookidwigitz.com');
    $eLog->log($customer->getName() . ' cancelled their order...');
    }
    }
    

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31. class Controller
    {
    public function newCustomer() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $msg = 'Sent welcome email to '.$customer->getName().
    ' at '.$customer->getEmail();
    $dLog->log($msg);
    $eLog = new EmailLogger('boss@demcrookidwigitz.com');
    $eLog->log($customer->getName() . ' has registered!');
    }
    public function createOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Created order ' . $number);
    $twitter = new Twitter('demcrookidwigitz', 'b3@tb0Xpr0$');
    $twitter->tweet($customer->getName().' just ordered from us!');
    }
    public function cancelOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Cancelled order number ' . $number);
    $eLog = new EmailLogger('boss@demcrookidwigitz.com');
    $eLog->log($customer->getName() . ' cancelled their order...');
    

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32. Your Codebase
    Is Growing
    

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33. ?
    

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34. class Controller
    {
    public function newCustomer() {
    $customer = new Customer($_POST);
    $email = new WelcomeEmail();
    $email->send($customer->getEmail());
    $dLog = new DiskLogger('/logs/prod.log');
    $msg = 'Sent welcome email to '.$customer->getName();
    $dLog->log($msg);
    $eLog = new EmailLogger('boss@demcrookidwigitz.com');
    $eLog->log($customer->getName() . ' has registered!');
    }
    public function createOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Created order ' . $number);
    $twitter = new Twitter('demcrookidwigitz', 'b3@tb0Xpr0$');
    $twitter->tweet($customer->getName() . ' just ordered from us!');
    }
    public function cancelOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Cancelled order number ' . $number);
    $eLog = new EmailLogger('boss@demcrookidwigitz.com');
    $eLog->log($customer->getName() . ' cancelled their order...');
    }
    }
    

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35. class Controller
    {
    public function newCustomer() {
    $customer = new Customer($_POST);
    $email = new WelcomeEmail();
    $email->send($customer->getEmail());
    $dLog = new DiskLogger('/logs/prod.log');
    $msg = 'Sent welcome email to '.$customer->getName();
    $dLog->log($msg);
    $eLog = new EmailLogger('boss@demcrookidwigitz.com');
    $eLog->log($customer->getName() . ' has registered!');
    }
    public function createOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Created order ' . $number);
    $twitter = new Twitter('demcrookidwigitz', 'b3@tb0Xpr0$');
    $twitter->tweet($customer->getName() . ' just ordered from us!');
    }
    public function cancelOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Cancelled order number ' . $number);
    $eLog = new EmailLogger('boss@demcrookidwigitz.com');
    $eLog->log($customer->getName() . ' cancelled their order...');
    }
    }
    

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36. class Controller
    {
    public function newCustomer() {
    $customer = new Customer($_POST);
    $email = new WelcomeEmail();
    $email->send($customer->getEmail());
    $dLog = new DiskLogger('/logs/prod.log');
    $msg = 'Sent welcome email to '.$customer->getName();
    $dLog->log($msg);
    $eLog = new EmailLogger('boss@demcrookidwigitz.com');
    $eLog->log($customer->getName() . ' has registered!');
    }
    public function createOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Created order ' . $number);
    $twitter = new Twitter('demcrookidwigitz', 'b3@tb0Xpr0$');
    $twitter->tweet($customer->getName() . ' just ordered from us!');
    }
    public function cancelOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Cancelled order number ' . $number);
    $eLog = new EmailLogger('boss@demcrookidwigitz.com');
    $eLog->log($customer->getName() . ' cancelled their order...');
    }
    }
    

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37. class Controller
    {
    public function newCustomer() {
    $customer = new Customer($_POST);
    $email = new WelcomeEmail();
    $email->send($customer->getEmail());
    $dLog = new DiskLogger('/logs/prod.log');
    $msg = 'Sent welcome email to '.$customer->getName();
    $dLog->log($msg);
    $eLog = new EmailLogger('boss@demcrookidwigitz.com');
    $eLog->log($customer->getName() . ' has registered!');
    }
    public function createOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Created order ' . $number);
    $twitter = new Twitter('demcrookidwigitz', 'b3@tb0Xpr0$');
    $twitter->tweet($customer->getName() . ' just ordered from us!');
    }
    public function cancelOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Cancelled order number ' . $number);
    $eLog = new EmailLogger('boss@demcrookidwigitz.com');
    $eLog->log($customer->getName() . ' cancelled their order...');
    }
    }
    

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38. Extensibility
    [A] system design principle where the implementation
    takes into consideration future growth.
    Extensibility - Wikipedia
    http://en.wikipedia.org/wiki/Extensibility
    

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39. class Controller
    {
    public function newCustomer() {
    $customer = new Customer($_POST);
    $email = new WelcomeEmail();
    $email->send($customer->getEmail());
    $dLog = new DiskLogger('/logs/prod.log');
    $msg = 'Sent welcome email to '.$customer->getName();
    $dLog->log($msg);
    $eLog = new EmailLogger('boss@demcrookidwigitz.com');
    $eLog->log($customer->getName() . ' has registered!');
    }
    public function createOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Created order ' . $number);
    $twitter = new Twitter('demcrookidwigitz', 'b3@tb0Xpr0$');
    $twitter->tweet($customer->getName() . ' just ordered from us!');
    }
    public function cancelOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Cancelled order number ' . $number);
    $eLog = new EmailLogger('boss@demcrookidwigitz.com');
    $eLog->log($customer->getName() . ' cancelled their order...');
    }
    }
    

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40. class Controller
    {
    public function newCustomer() {
    $customer = new Customer($_POST);
    $email = new WelcomeEmail();
    $email->send($customer->getEmail());
    $dLog = new DiskLogger('/logs/prod.log');
    $msg = 'Sent welcome email to '.$customer->getName();
    $dLog->log($msg);
    $eLog = new EmailLogger('boss@demcrookidwigitz.com');
    $eLog->log($customer->getName() . ' has registered!');
    }
    public function createOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Created order ' . $number);
    $twitter = new Twitter('demcrookidwigitz', 'b3@tb0Xpr0$');
    $twitter->tweet($customer->getName() . ' just ordered from us!');
    }
    public function cancelOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Cancelled order number ' . $number);
    $eLog = new EmailLogger('boss@demcrookidwigitz.com');
    $eLog->log($customer->getName() . ' cancelled their order...');
    }
    }
    NOT EXTENSIBLE!
    

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41. Model
    View
    Controller
    

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42. What is the
    Responsibility
    of a Controller?
    

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43. Controllers should
    contain
    LOGIC
    

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44. Controllers should
    contain
    LOGIC
    

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45. Controllers should
    contain
    LOGIC
    

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46. Controllers as Glue
    Custom
    Application
    Code
    Framework Controller
    

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47. Controllers as Glue
    Custom
    Application
    Code
    Controller
    

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48. Controllers as Glue
    Custom
    Application
    Code
    Controller
    

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49. Event Dispatcher
    

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50. Event Dispatcher - Concept
    Request
    Response
    kernel.controller
    kernel.request
    kernel.response
    kernel.view
    

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51. Event Dispatcher - Concept
    Request
    Response
    Your Events
    kernel.controller
    kernel.request
    kernel.response
    kernel.view
    

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52. Event Dispatcher - Concept
    Request
    Response
    kernel.controller
    kernel.request
    kernel.response
    kernel.view
    user.login
    

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53. Event Dispatcher - Concept
    Request
    Response
    kernel.controller
    kernel.request
    kernel.response
    kernel.view
    user.login
    user.register
    

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54. Event Dispatcher - Concept
    Request
    Response
    kernel.controller
    kernel.request
    kernel.response
    kernel.view
    user.login
    user.register
    $user
    

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55. Event Dispatcher - Concept
    Request
    Response
    kernel.controller
    kernel.request
    kernel.response
    kernel.view
    user.login
    user.register
    $user
    $user
    

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56. Event Dispatcher - Register Listeners
    EventDispatcher
    AListener
    named.eventA
    BListener
    named.eventB
    CListener
    named.eventC
    

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57. Let’s use a
    more concrete
    example
    

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58. Event Dispatcher - Register Listeners
    CartListener::
    onAddToCart()
    EventDispatcher
    cart.add
    CustomerListener::
    onRegister()
    customer.register
    CartListener::
    grantDiscount()
    cart.checkout
    

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59. Event Dispatcher - Register Listeners
    use Symfony\Component\EventDispatcher\EventDispatcher;
    $dispatcher = new EventDispatcher();
    $listener = new CustomerListener();
    $dispatcher->addListener('customer.register', array($listener, 'onRegister'));
    // Register more listeners
    class CustomerListener
    {
    public function onRegister(CustomerEvent $event)
    {
    // Do some work
    }
    }
    Any PHP Callable
    true === is_callable()
    

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60. Event Dispatcher - Register Listeners
    use Symfony\Component\EventDispatcher\EventDispatcher;
    $dispatcher = new EventDispatcher();
    $dispatcher->addListener('customer.register', array('CustomerListener', 'onRegister'));
    // Register more listeners
    class CustomerListener
    {
    public static function onRegister(CustomerEvent $event)
    {
    // Do some work
    }
    }
    

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61. Event Dispatcher - Register Listeners
    use Symfony\Component\EventDispatcher\EventDispatcher;
    $dispatcher = new EventDispatcher();
    $dispatcher->addListener('customer.register', function(CustomerEvent $event) {
    // Do some work
    });
    

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62. Event Dispatcher - Dispatch an Event
    

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63. Request
    Response
    Event Dispatcher - Dispatch an Event
    

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64. Request
    Response
    Event Dispatcher - Dispatch an Event
    EventDispatcher
    “customer.register”
    CustomerListener::
    onRegister()
    “cart.add”
    CartListener::
    onAddToCart()
    “cart.checkout”
    CartListener::
    grantDiscount()
    

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65. Request
    Response
    CustomerEvent
    “customer.register”
    Customer
    Event Dispatcher - Dispatch an Event
    EventDispatcher
    “customer.register”
    CustomerListener::
    onRegister()
    “cart.add”
    CartListener::
    onAddToCart()
    “cart.checkout”
    CartListener::
    grantDiscount()
    

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66. Request
    Response
    CustomerEvent
    “customer.register”
    Customer
    Event Dispatcher - Dispatch an Event
    EventDispatcher
    “customer.register”
    CustomerListener::
    onRegister()
    “cart.add”
    CartListener::
    onAddToCart()
    “cart.checkout”
    CartListener::
    grantDiscount()
    

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67. Event Dispatcher - Dispatch an Event
    use Symfony\Component\EventDispatcher\EventDispatcher;
    class CustomerController
    {
    public function __construct(EventDispatcher $dispatcher) {
    $this->dispatcher = $dispatcher;
    }
    public function newCustomer() {
    $customer = new Customer(array(
    'first_name' => 'Bob',
    'last_name' => 'Smith',
    'email' => 'bobsmith@gmail.com',
    ));
    $event = new CustomerEvent($customer);
    $this->dispatcher->dispatch('customer.register', $event);
    }
    }
    Customer
    Event
    Event Name
    

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68. Request
    Response
    CustomerEvent
    “customer.register”
    Customer
    Event Dispatcher - Dispatch an Event
    EventDispatcher
    “customer.register”
    CustomerListener::
    onRegister()
    “cart.add”
    CartListener::
    onAddToCart()
    “cart.checkout”
    CartListener::
    grantDiscount()
    

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69. Request
    Response
    CustomerEvent
    “customer.register”
    Customer
    Event Dispatcher - Dispatch an Event
    EventDispatcher
    “customer.register”
    CustomerListener::
    onRegister()
    “cart.add”
    CartListener::
    onAddToCart()
    “cart.checkout”
    CartListener::
    grantDiscount()
    $this->dispatcher->dispatch('customer.register', $event);
    

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70. Request
    Response
    CustomerEvent
    “customer.register”
    Customer
    Event Dispatcher - Dispatch an Event
    EventDispatcher
    “customer.register”
    CustomerListener::
    onRegister()
    “cart.add”
    CartListener::
    onAddToCart()
    “cart.checkout”
    CartListener::
    grantDiscount()
    

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71. Request
    Response
    CustomerEvent
    “customer.register”
    Customer
    Event Dispatcher - Dispatch an Event
    EventDispatcher
    “customer.register”
    CustomerListener::
    onRegister()
    “cart.add”
    CartListener::
    onAddToCart()
    “cart.checkout”
    CartListener::
    grantDiscount()
    “customer.register”
    CustomerListener::
    onRegister()
    

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72. Event Dispatcher - Handle the Event
    class CustomerListener
    {
    public function onRegister(CustomerEvent $event)
    {
    $customer = $event->getCustomer();
    $name = $event->getName();
    $dispatcher = $event->getDispatcher();
    // Do something with Customer object
    }
    }
    CustomerEvent
    “customer.register”
    Customer
    

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73. Event Dispatcher - Handle the Event
    class CustomerListener
    {
    public function onRegister(CustomerEvent $event)
    {
    $customer = $event->getCustomer();
    $name = $event->getName();
    $dispatcher = $event->getDispatcher();
    // Do something with Customer object
    }
    }
    

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74. Event Dispatcher - Handle the Event
    use Symfony\Component\EventDispatcher\Event;
    class CustomerEvent extends Event
    {
    protected $customer;
    public function __construct(Customer $customer) {
    $this->customer = $customer;
    }
    public function getCustomer() {
    return $this->customer;
    }
    }
    

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75. Event Dispatcher - All together now!
    

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76. Event Dispatcher - All together now!
    EventDispatcher
    

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77. Event Dispatcher - All together now!
    CartListener::
    onAddToCart()
    CustomerListener::
    onRegister()
    CartListener::
    grantDiscount()
    EventDispatcher
    cart.checkout
    cart.add
    customer.register
    

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78. Event Dispatcher - All together now!
    CartListener::
    onAddToCart()
    CustomerListener::
    onRegister()
    CartListener::
    grantDiscount()
    EventDispatcher
    “cart.checkout”
    CartListener::
    grantDiscount()
    “cart.add”
    CartListener::
    onAddToCart()
    “customer.register”
    CustomerListener::
    onRegister()
    

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79. CustomerEvent
    “customer.register”
    Customer
    Event Dispatcher - All together now!
    CartListener::
    onAddToCart()
    CustomerListener::
    onRegister()
    CartListener::
    grantDiscount()
    EventDispatcher
    “cart.checkout”
    CartListener::
    grantDiscount()
    “cart.add”
    CartListener::
    onAddToCart()
    “customer.register”
    CustomerListener::
    onRegister()
    

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80. CustomerEvent
    “customer.register”
    Customer
    Event Dispatcher - All together now!
    CartListener::
    onAddToCart()
    CustomerListener::
    onRegister()
    CartListener::
    grantDiscount()
    EventDispatcher
    “cart.checkout”
    CartListener::
    grantDiscount()
    “cart.add”
    CartListener::
    onAddToCart()
    “customer.register”
    CustomerListener::
    onRegister()
    $this->dispatcher->dispatch('customer.register', $event);
    

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81. CustomerEvent
    “customer.register”
    Customer
    Event Dispatcher - All together now!
    CartListener::
    onAddToCart()
    CustomerListener::
    onRegister()
    CartListener::
    grantDiscount()
    EventDispatcher
    “cart.checkout”
    CartListener::
    grantDiscount()
    “cart.add”
    CartListener::
    onAddToCart()
    “customer.register”
    CustomerListener::
    onRegister()
    

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82. CustomerEvent
    “customer.register”
    Customer
    Event Dispatcher - All together now!
    CartListener::
    onAddToCart()
    CustomerListener::
    onRegister()
    CartListener::
    grantDiscount()
    EventDispatcher
    “cart.checkout”
    CartListener::
    grantDiscount()
    “cart.add”
    CartListener::
    onAddToCart()
    “customer.register”
    CustomerListener::
    onRegister()
    “customer.register”
    CustomerListener::
    onRegister()
    

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83. CustomerEvent
    “customer.register”
    Customer
    Event Dispatcher - All together now!
    CartListener::
    onAddToCart()
    CustomerListener::
    onRegister()
    CartListener::
    grantDiscount()
    EventDispatcher
    “cart.checkout”
    CartListener::
    grantDiscount()
    “cart.add”
    CartListener::
    onAddToCart()
    “customer.register”
    CustomerListener::
    onRegister()
    “customer.register”
    CustomerListener::
    onRegister()
    That’s
    Event Dispatcher!
    

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84. Let’s refactor
    our Controller
    

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85. class Controller
    {
    public function newCustomer() {
    $customer = new Customer($_POST);
    $email = new WelcomeEmail();
    $email->send($customer->getEmail());
    $dLog = new DiskLogger('/logs/prod.log');
    $msg = 'Sent welcome email to '.$customer->getName();
    $dLog->log($msg);
    $eLog = new EmailLogger('boss@demcrookidwigitz.com');
    $eLog->log($customer->getName() . ' has registered!');
    }
    public function createOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Created order ' . $number);
    $twitter = new Twitter('demcrookidwigitz', 'b3@tb0Xpr0$');
    $twitter->tweet($customer->getName() . ' just ordered from us!');
    }
    public function cancelOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Cancelled order number ' . $number);
    $eLog = new EmailLogger('boss@demcrookidwigitz.com');
    $eLog->log($customer->getName() . ' cancelled their order...');
    }
    }
    START
    

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86. class Controller
    {
    public function __construct(EventDispatcher $dispatcher) {
    $this->dispatcher = $dispatcher;
    }
    public function newCustomer() {
    $customer = new Customer($_POST);
    $event = new CustomerEvent($customer);
    $this->dispatcher->dispatch('customer.register', $event);
    }
    public function createOrder() {
    // ...
    $event = new OrderEvent($order);
    $this->dispatcher->dispatch('order.new', $event);
    $event = new CustomerEvent($customer);
    $this->dispatcher->dispatch('customer.order.new', $event);
    }
    public function cancelOrder() {
    // ...
    $event = new OrderEvent($order);
    $this->dispatcher->dispatch('order.cancel', $event);
    $event = new CustomerEvent($customer);
    $this->dispatcher->dispatch('customer.order.cancel', $event);
    }
    }
    FINISH
    

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87. 6
    Inject the EventDispatcher
    

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88. class Controller
    {
    public function __construct(EventDispatcher $dispatcher) {
    $this->dispatcher = $dispatcher;
    }
    public function newCustomer() {
    $customer = new Customer($_POST);
    $email = new WelcomeEmail();
    $email->send($customer->getEmail());
    $dLog = new DiskLogger('/logs/prod.log');
    $msg = 'Sent welcome email to '.$customer->getName();
    $dLog->log($msg);
    $eLog = new EmailLogger('boss@demcrookidwigitz.com');
    $eLog->log($customer->getName() . ' has registered!');
    }
    public function createOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Created order ' . $number);
    $twitter = new Twitter('demcrookidwigitz', 'b3@tb0Xpr0$');
    $twitter->tweet($customer->getName() . ' just ordered from us!');
    }
    public function cancelOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Cancelled order number ' . $number);
    $eLog = new EmailLogger('boss@demcrookidwigitz.com');
    

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89. 7Our First Event
    

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90. class Controller
    {
    public function __construct(EventDispatcher $dispatcher) {
    $this->dispatcher = $dispatcher;
    }
    public function newCustomer() {
    $customer = new Customer($_POST);
    $email = new WelcomeEmail();
    $email->send($customer->getEmail());
    $dLog = new DiskLogger('/logs/prod.log');
    $msg = 'Sent welcome email to '.$customer->getName();
    $dLog->log($msg);
    $eLog = new EmailLogger('boss@demcrookidwigitz.com');
    $eLog->log($customer->getName() . ' has registered!');
    }
    public function createOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Created order ' . $number);
    $twitter = new Twitter('demcrookidwigitz', 'b3@tb0Xpr0$');
    $twitter->tweet($customer->getName() . ' just ordered from us!');
    }
    public function cancelOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Cancelled order number ' . $number);
    $eLog = new EmailLogger('boss@demcrookidwigitz.com');
    

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91. class Controller
    {
    public function __construct(EventDispatcher $dispatcher) {
    $this->dispatcher = $dispatcher;
    }
    public function newCustomer() {
    $customer = new Customer($_POST);
    $event = new CustomerEvent($customer);
    $this->dispatcher->dispatch('customer.register', $event);
    $dLog = new DiskLogger('/logs/prod.log');
    $msg = 'Sent welcome email to '.$customer->getName();
    $dLog->log($msg);
    $eLog = new EmailLogger('boss@demcrookidwigitz.com');
    $eLog->log($customer->getName() . ' has registered!');
    }
    public function createOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Created order ' . $number);
    $twitter = new Twitter('demcrookidwigitz', 'b3@tb0Xpr0$');
    $twitter->tweet($customer->getName() . ' just ordered from us!');
    }
    public function cancelOrder() {
    // ...
    $dLog = new DiskLogger('/logs/prod.log');
    $dLog->log('Cancelled order number ' . $number);
    $eLog = new EmailLogger('boss@demcrookidwigitz.com');
    

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92. use Symfony\Component\EventDispatcher\Event;
    class CustomerEvent extends Event
    {
    protected $customer;
    public function __construct(Customer $customer) {
    $this->customer = $customer;
    }
    public function getCustomer() {
    return $this->customer;
    }
    }
    

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93. use Symfony\Component\EventDispatcher\EventDispatcher;
    $dispatcher = new EventDispatcher();
    // Wire listeners
    $listener = new CustomerEmailListener(new WelcomeEmail());
    $dispatcher->addListener('customer.register', array($listener, 'onRegister'));
    class WelcomeEmail
    {
    public function send($to, $name) {
    return mail($to, $this->getSubject(), $this->getMessage($name), $this->getHeaders());
    }
    protected function getSubject() {
    return 'New Account';
    }
    protected function getMessage($name) {
    return "Welcome " . $name . "!
    Your new space has been created! Use this link to login:
    https://activate.demcrookidwigitz.com/code/Sq9284tWBnWgpjw
    Thanks!
    DemCrookidWigitz";
    }
    protected function getHeaders() {
    $headers = array();
    $headers[] = 'From: accounts@demcrookidwigitz.com';
    

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94. use Symfony\Component\EventDispatcher\EventDispatcher;
    $dispatcher = new EventDispatcher();
    // Wire listeners
    $listener = new CustomerEmailListener(new WelcomeEmail());
    $dispatcher->addListener('customer.register', array($listener, 'onRegister'));
    

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95. use Symfony\Component\EventDispatcher\EventDispatcher;
    $dispatcher = new EventDispatcher();
    // Wire listeners
    $listener = new CustomerEmailListener(new WelcomeEmail());
    $dispatcher->addListener('customer.register', array($listener, 'onRegister'));
    

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96. use Symfony\Component\EventDispatcher\EventDispatcher;
    $dispatcher = new EventDispatcher();
    // Wire listeners
    $listener = new CustomerEmailListener(new WelcomeEmail());
    $dispatcher->addListener('customer.register', array($listener, 'onRegister'));
    class CustomerEmailListener
    {
    public function __construct(WelcomeEmail $email) {
    $this->email = $email;
    }
    public function onRegister(CustomerEvent $event) {
    $customer = $event->getCustomer();
    $this->email->send($customer->getEmail(), $customer->getName());
    }
    }
    

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97. use Symfony\Component\EventDispatcher\EventDispatcher;
    $dispatcher = new EventDispatcher();
    // Wire listeners
    $listener = new CustomerEmailListener(new WelcomeEmail());
    $dispatcher->addListener('customer.register', array($listener, 'onRegister'));
    class CustomerEmailListener
    {
    public function __construct(WelcomeEmail $email) {
    $this->email = $email;
    }
    public function onRegister(CustomerEvent $event) {
    $customer = $event->getCustomer();
    $this->email->send($customer->getEmail(), $customer->getName());
    }
    }
    

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98. use Symfony\Component\EventDispatcher\EventDispatcher;
    $dispatcher = new EventDispatcher();
    // Wire listeners
    $listener = new CustomerEmailListener(new WelcomeEmail());
    $dispatcher->addListener('customer.register', array($listener, 'onRegister'));
    class CustomerEmailListener
    {
    public function __construct(WelcomeEmail $email) {
    $this->email = $email;
    }
    public function onRegister(CustomerEvent $event) {
    $customer = $event->getCustomer();
    $this->email->send($customer->getEmail(), $customer->getName());
    }
    }
    class WelcomeEmail
    {
    public function send($to, $name) {
    return mail($to, $this->getSubject(), $this->getMessage($name), $this->getHeaders());
    }
    }
    

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99. use Symfony\Component\EventDispatcher\EventDispatcher;
    $dispatcher = new EventDispatcher();
    // Wire listeners
    $listener = new CustomerEmailListener(new WelcomeEmail());
    $dispatcher->addListener('customer.register', array($listener, 'onRegister'));
    class CustomerEmailListener
    {
    public function __construct(WelcomeEmail $email) {
    $this->email = $email;
    }
    public function onRegister(CustomerEvent $event) {
    $customer = $event->getCustomer();
    $this->email->send($customer->getEmail(), $customer->getName());
    }
    }
    class WelcomeEmail
    {
    public function send($to, $name) {
    return mail($to, $this->getSubject(), $this->getMessage($name), $this->getHeaders());
    }
    }
    

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100. 8
     Move more code to listeners
     

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101. class Controller
     {
     public function __construct(EventDispatcher $dispatcher) {
     $this->dispatcher = $dispatcher;
     }
     public function newCustomer() {
     $customer = new Customer($_POST);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.register', $event);
     $dLog = new DiskLogger('/logs/prod.log');
     $msg = 'Sent welcome email to '.$customer->getName();
     $dLog->log($msg);
     $eLog = new EmailLogger('boss@demcrookidwigitz.com');
     $eLog->log($customer->getName() . ' has registered!');
     }
     public function createOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Created order ' . $number);
     $twitter = new Twitter('demcrookidwigitz', 'b3@tb0Xpr0$');
     $twitter->tweet($customer->getName() . ' just ordered from us!');
     }
     public function cancelOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Cancelled order number ' . $number);
     $eLog = new EmailLogger('boss@demcrookidwigitz.com');
     

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102. use Symfony\Component\EventDispatcher\EventDispatcher;
     $dispatcher = new EventDispatcher();
     $diskLogger = new DiskLogger('/logs/prod.log');
     // Wire listeners
     $listener = new CustomerEmailListener(new WelcomeEmail(), $diskLogger);
     $dispatcher->addListener('customer.register', array($listener, 'onRegister'));
     

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103. use Symfony\Component\EventDispatcher\EventDispatcher;
     $dispatcher = new EventDispatcher();
     $diskLogger = new DiskLogger('/logs/prod.log');
     // Wire listeners
     $listener = new CustomerEmailListener(new WelcomeEmail(), $diskLogger);
     $dispatcher->addListener('customer.register', array($listener, 'onRegister'));
     

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104. use Symfony\Component\EventDispatcher\EventDispatcher;
     $dispatcher = new EventDispatcher();
     $diskLogger = new DiskLogger('/logs/prod.log');
     // Wire listeners
     $listener = new CustomerEmailListener(new WelcomeEmail(), $diskLogger);
     $dispatcher->addListener('customer.register', array($listener, 'onRegister'));
     class CustomerEmailListener
     {
     public function __construct(WelcomeEmail $email) {
     $this->email = $email;
     }
     public function onRegister(CustomerEvent $event) {
     $customer = $event->getCustomer();
     $this->email->send($customer->getEmail(), $customer->getName());
     }
     }
     

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105. use Symfony\Component\EventDispatcher\EventDispatcher;
     $dispatcher = new EventDispatcher();
     $diskLogger = new DiskLogger('/logs/prod.log');
     // Wire listeners
     $listener = new CustomerEmailListener(new WelcomeEmail(), $diskLogger);
     $dispatcher->addListener('customer.register', array($listener, 'onRegister'));
     class CustomerEmailListener
     {
     public function __construct(WelcomeEmail $email) {
     $this->email = $email;
     }
     public function onRegister(CustomerEvent $event) {
     $customer = $event->getCustomer();
     $this->email->send($customer->getEmail(), $customer->getName());
     }
     }
     class CustomerEmailListener
     {
     public function __construct(WelcomeEmail $email, DiskLogger $logger) {
     $this->email = $email;
     $this->logger = $logger;
     }
     public function onRegister(CustomerEvent $event) {
     $customer = $event->getCustomer();
     $this->email->send($customer->getEmail(), $customer->getName());
     }
     }
     

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106. use Symfony\Component\EventDispatcher\EventDispatcher;
     $dispatcher = new EventDispatcher();
     $diskLogger = new DiskLogger('/logs/prod.log');
     // Wire listeners
     $listener = new CustomerEmailListener(new WelcomeEmail(), $diskLogger);
     $dispatcher->addListener('customer.register', array($listener, 'onRegister'));
     class CustomerEmailListener
     {
     public function __construct(WelcomeEmail $email) {
     $this->email = $email;
     }
     public function onRegister(CustomerEvent $event) {
     $customer = $event->getCustomer();
     $this->email->send($customer->getEmail(), $customer->getName());
     }
     }
     class CustomerEmailListener
     {
     public function __construct(WelcomeEmail $email, DiskLogger $logger) {
     $this->email = $email;
     $this->logger = $logger;
     }
     public function onRegister(CustomerEvent $event) {
     $customer = $event->getCustomer();
     $this->email->send($customer->getEmail(), $customer->getName());
     }
     }
     

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107. use Symfony\Component\EventDispatcher\EventDispatcher;
     $dispatcher = new EventDispatcher();
     $diskLogger = new DiskLogger('/logs/prod.log');
     // Wire listeners
     $listener = new CustomerEmailListener(new WelcomeEmail(), $diskLogger);
     $dispatcher->addListener('customer.register', array($listener, 'onRegister'));
     class CustomerEmailListener
     {
     public function __construct(WelcomeEmail $email) {
     $this->email = $email;
     }
     public function onRegister(CustomerEvent $event) {
     $customer = $event->getCustomer();
     $this->email->send($customer->getEmail(), $customer->getName());
     }
     }
     class CustomerEmailListener
     {
     public function __construct(WelcomeEmail $email, DiskLogger $logger) {
     $this->email = $email;
     $this->logger = $logger;
     }
     public function onRegister(CustomerEvent $event) {
     $customer = $event->getCustomer();
     $this->email->send($customer->getEmail(), $customer->getName());
     }
     }
     class CustomerEmailListener
     {
     public function __construct(WelcomeEmail $email, DiskLogger $logger) {
     $this->email = $email;
     $this->logger = $logger;
     }
     public function onRegister(CustomerEvent $event) {
     $customer = $event->getCustomer();
     $this->email->send($customer->getEmail(), $customer->getName());
     $this->logger->log('Sent welcome email to ' . $customer->getName());
     }
     }
     

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108. use Symfony\Component\EventDispatcher\EventDispatcher;
     $dispatcher = new EventDispatcher();
     $diskLogger = new DiskLogger('/logs/prod.log');
     // Wire listeners
     $listener = new CustomerEmailListener(new WelcomeEmail(), $diskLogger);
     $dispatcher->addListener('customer.register', array($listener, 'onRegister'));
     class CustomerEmailListener
     {
     public function __construct(WelcomeEmail $email) {
     $this->email = $email;
     }
     public function onRegister(CustomerEvent $event) {
     $customer = $event->getCustomer();
     $this->email->send($customer->getEmail(), $customer->getName());
     }
     }
     class CustomerEmailListener
     {
     public function __construct(WelcomeEmail $email, DiskLogger $logger) {
     $this->email = $email;
     $this->logger = $logger;
     }
     public function onRegister(CustomerEvent $event) {
     $customer = $event->getCustomer();
     $this->email->send($customer->getEmail(), $customer->getName());
     }
     }
     class CustomerEmailListener
     {
     public function __construct(WelcomeEmail $email, DiskLogger $logger) {
     $this->email = $email;
     $this->logger = $logger;
     }
     public function onRegister(CustomerEvent $event) {
     $customer = $event->getCustomer();
     $this->email->send($customer->getEmail(), $customer->getName());
     $this->logger->log('Sent welcome email to ' . $customer->getName());
     }
     }
     

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109. class Controller
     {
     public function __construct(EventDispatcher $dispatcher) {
     $this->dispatcher = $dispatcher;
     }
     public function newCustomer() {
     $customer = new Customer($_POST);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.register', $event);
     $dLog = new DiskLogger('/logs/prod.log');
     $msg = 'Sent welcome email to '.$customer->getName();
     $dLog->log($msg);
     $eLog = new EmailLogger('boss@demcrookidwigitz.com');
     $eLog->log($customer->getName() . ' has registered!');
     }
     public function createOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Created order ' . $number);
     $twitter = new Twitter('demcrookidwigitz', 'b3@tb0Xpr0$');
     $twitter->tweet($customer->getName() . ' just ordered from us!');
     }
     public function cancelOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Cancelled order number ' . $number);
     $eLog = new EmailLogger('boss@demcrookidwigitz.com');
     

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110. class Controller
     {
     public function __construct(EventDispatcher $dispatcher) {
     $this->dispatcher = $dispatcher;
     }
     public function newCustomer() {
     $customer = new Customer($_POST);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.register', $event);
     $dLog = new DiskLogger('/logs/prod.log');
     $msg = 'Sent welcome email to '.$customer->getName();
     $dLog->log($msg);
     $eLog = new EmailLogger('boss@demcrookidwigitz.com');
     $eLog->log($customer->getName() . ' has registered!');
     }
     public function createOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Created order ' . $number);
     $twitter = new Twitter('demcrookidwigitz', 'b3@tb0Xpr0$');
     $twitter->tweet($customer->getName() . ' just ordered from us!');
     }
     public function cancelOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Cancelled order number ' . $number);
     $eLog = new EmailLogger('boss@demcrookidwigitz.com');
     class Controller
     {
     public function __construct(EventDispatcher $dispatcher) {
     $this->dispatcher = $dispatcher;
     }
     public function newCustomer() {
     $customer = new Customer($_POST);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.register', $event);
     $eLog = new EmailLogger('boss@demcrookidwigitz.com');
     $eLog->log($customer->getName() . ' has registered!');
     }
     public function createOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Created order ' . $number);
     $twitter = new Twitter('demcrookidwigitz', 'b3@tb0Xpr0$');
     $twitter->tweet($customer->getName() . ' just ordered from us!');
     }
     public function cancelOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Cancelled order number ' . $number);
     $eLog = new EmailLogger('boss@demcrookidwigitz.com');
     $eLog->log($customer->getName() . ' cancelled their order...');
     }
     }
     

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111. class Controller
     {
     public function __construct(EventDispatcher $dispatcher) {
     $this->dispatcher = $dispatcher;
     }
     public function newCustomer() {
     $customer = new Customer($_POST);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.register', $event);
     $dLog = new DiskLogger('/logs/prod.log');
     $msg = 'Sent welcome email to '.$customer->getName();
     $dLog->log($msg);
     $eLog = new EmailLogger('boss@demcrookidwigitz.com');
     $eLog->log($customer->getName() . ' has registered!');
     }
     public function createOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Created order ' . $number);
     $twitter = new Twitter('demcrookidwigitz', 'b3@tb0Xpr0$');
     $twitter->tweet($customer->getName() . ' just ordered from us!');
     }
     public function cancelOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Cancelled order number ' . $number);
     $eLog = new EmailLogger('boss@demcrookidwigitz.com');
     class Controller
     {
     public function __construct(EventDispatcher $dispatcher) {
     $this->dispatcher = $dispatcher;
     }
     public function newCustomer() {
     $customer = new Customer($_POST);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.register', $event);
     $eLog = new EmailLogger('boss@demcrookidwigitz.com');
     $eLog->log($customer->getName() . ' has registered!');
     }
     public function createOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Created order ' . $number);
     $twitter = new Twitter('demcrookidwigitz', 'b3@tb0Xpr0$');
     $twitter->tweet($customer->getName() . ' just ordered from us!');
     }
     public function cancelOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Cancelled order number ' . $number);
     $eLog = new EmailLogger('boss@demcrookidwigitz.com');
     $eLog->log($customer->getName() . ' cancelled their order...');
     }
     }
     

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112. use Symfony\Component\EventDispatcher\EventDispatcher;
     $dispatcher = new EventDispatcher();
     $bossEmail = 'boss@demcrookidwigitz.com';
     // Wire listeners
     // ...
     $listener = new BossNewCustomerEmailListener(new BossNewCustomerEmail($bossEmail));
     $dispatcher->addListener('customer.register', array($listener, 'onCustomerRegister'));
     

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113. use Symfony\Component\EventDispatcher\EventDispatcher;
     $dispatcher = new EventDispatcher();
     $bossEmail = 'boss@demcrookidwigitz.com';
     // Wire listeners
     // ...
     $listener = new BossNewCustomerEmailListener(new BossNewCustomerEmail($bossEmail));
     $dispatcher->addListener('customer.register', array($listener, 'onCustomerRegister'));
     

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114. use Symfony\Component\EventDispatcher\EventDispatcher;
     $dispatcher = new EventDispatcher();
     $bossEmail = 'boss@demcrookidwigitz.com';
     // Wire listeners
     // ...
     $listener = new BossNewCustomerEmailListener(new BossNewCustomerEmail($bossEmail));
     $dispatcher->addListener('customer.register', array($listener, 'onCustomerRegister'));
     

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115. use Symfony\Component\EventDispatcher\EventDispatcher;
     $dispatcher = new EventDispatcher();
     $bossEmail = 'boss@demcrookidwigitz.com';
     // Wire listeners
     // ...
     $listener = new BossNewCustomerEmailListener(new BossNewCustomerEmail($bossEmail));
     $dispatcher->addListener('customer.register', array($listener, 'onCustomerRegister'));
     class BossNewCustomerEmail
     {
     public function __construct($bossEmail) {
     $this->bossEmail = $bossEmail;
     }
     public function send($name) {
     return mail($this->bossEmail, $this->getSubject(), $this->getMessage($name),
     $this->getHeaders());
     }
     protected function getSubject() {
     return 'New Customer Registered!';
     }
     protected function getMessage($name) {
     return "Boss! " . $name . " just registered! Sweet, huh?";
     }
     // ...
     }
     

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116. use Symfony\Component\EventDispatcher\EventDispatcher;
     $dispatcher = new EventDispatcher();
     $bossEmail = 'boss@demcrookidwigitz.com';
     // Wire listeners
     // ...
     $listener = new BossNewCustomerEmailListener(new BossNewCustomerEmail($bossEmail));
     $dispatcher->addListener('customer.register', array($listener, 'onCustomerRegister'));
     

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117. use Symfony\Component\EventDispatcher\EventDispatcher;
     $dispatcher = new EventDispatcher();
     $bossEmail = 'boss@demcrookidwigitz.com';
     // Wire listeners
     // ...
     $listener = new BossNewCustomerEmailListener(new BossNewCustomerEmail($bossEmail));
     $dispatcher->addListener('customer.register', array($listener, 'onCustomerRegister'));
     class BossNewCustomerEmailListener
     {
     public function __construct(BossNewCustomerEmail $email) {
     $this->email = $email;
     }
     public function onCustomerRegister(CustomerEvent $event) {
     $customer = $event->getCustomer();
     $this->email->send($customer->getName());
     }
     }
     

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118. use Symfony\Component\EventDispatcher\EventDispatcher;
     $dispatcher = new EventDispatcher();
     $bossEmail = 'boss@demcrookidwigitz.com';
     // Wire listeners
     // ...
     $listener = new BossNewCustomerEmailListener(new BossNewCustomerEmail($bossEmail));
     $dispatcher->addListener('customer.register', array($listener, 'onCustomerRegister'));
     class BossNewCustomerEmailListener
     {
     public function __construct(BossNewCustomerEmail $email) {
     $this->email = $email;
     }
     public function onCustomerRegister(CustomerEvent $event) {
     $customer = $event->getCustomer();
     $this->email->send($customer->getName());
     }
     }
     

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119. class Controller
     {
     public function __construct(EventDispatcher $dispatcher) {
     $this->dispatcher = $dispatcher;
     }
     public function newCustomer() {
     $customer = new Customer($_POST);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.register', $event);
     $eLog = new EmailLogger('boss@demcrookidwigitz.com');
     $eLog->log($customer->getName() . ' has registered!');
     }
     public function createOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Created order ' . $number);
     $twitter = new Twitter('demcrookidwigitz', 'b3@tb0Xpr0$');
     $twitter->tweet($customer->getName() . ' just ordered from us!');
     }
     public function cancelOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Cancelled order number ' . $number);
     $eLog = new EmailLogger('boss@demcrookidwigitz.com');
     $eLog->log($customer->getName() . ' cancelled their order...');
     }
     }
     

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120. class Controller
     {
     public function __construct(EventDispatcher $dispatcher) {
     $this->dispatcher = $dispatcher;
     }
     public function newCustomer() {
     $customer = new Customer($_POST);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.register', $event);
     $eLog = new EmailLogger('boss@demcrookidwigitz.com');
     $eLog->log($customer->getName() . ' has registered!');
     }
     public function createOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Created order ' . $number);
     $twitter = new Twitter('demcrookidwigitz', 'b3@tb0Xpr0$');
     $twitter->tweet($customer->getName() . ' just ordered from us!');
     }
     public function cancelOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Cancelled order number ' . $number);
     $eLog = new EmailLogger('boss@demcrookidwigitz.com');
     $eLog->log($customer->getName() . ' cancelled their order...');
     }
     }
     class Controller
     {
     public function __construct(EventDispatcher $dispatcher) {
     $this->dispatcher = $dispatcher;
     }
     public function newCustomer() {
     $customer = new Customer($_POST);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.register', $event);
     }
     public function createOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Created order ' . $number);
     $twitter = new Twitter('demcrookidwigitz', 'b3@tb0Xpr0$');
     $twitter->tweet($customer->getName() . ' just ordered from us!');
     }
     public function cancelOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Cancelled order number ' . $number);
     $eLog = new EmailLogger('boss@demcrookidwigitz.com');
     $eLog->log($customer->getName() . ' cancelled their order...');
     }
     }
     

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121. 9
     Clean Up Other Controllers
     

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122. class Controller
     {
     public function __construct(EventDispatcher $dispatcher) {
     $this->dispatcher = $dispatcher;
     }
     public function newCustomer() {
     $customer = new Customer($_POST);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.register', $event);
     }
     public function createOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Created order ' . $number);
     $twitter = new Twitter('demcrookidwigitz', 'b3@tb0Xpr0$');
     $twitter->tweet($customer->getName() . ' just ordered from us!');
     }
     public function cancelOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Cancelled order number ' . $number);
     $eLog = new EmailLogger('boss@demcrookidwigitz.com');
     $eLog->log($customer->getName() . ' cancelled their order...');
     }
     }
     

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123. class Controller
     {
     public function __construct(EventDispatcher $dispatcher) {
     $this->dispatcher = $dispatcher;
     }
     public function newCustomer() {
     $customer = new Customer($_POST);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.register', $event);
     }
     public function createOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Created order ' . $number);
     $twitter = new Twitter('demcrookidwigitz', 'b3@tb0Xpr0$');
     $twitter->tweet($customer->getName() . ' just ordered from us!');
     }
     public function cancelOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Cancelled order number ' . $number);
     $eLog = new EmailLogger('boss@demcrookidwigitz.com');
     $eLog->log($customer->getName() . ' cancelled their order...');
     }
     }
     class Controller
     {
     public function __construct(EventDispatcher $dispatcher) {
     $this->dispatcher = $dispatcher;
     }
     public function newCustomer() {
     $customer = new Customer($_POST);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.register', $event);
     }
     public function createOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Created order ' . $number);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.order.new', $event);
     }
     public function cancelOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Cancelled order number ' . $number);
     $eLog = new EmailLogger('boss@demcrookidwigitz.com');
     $eLog->log($customer->getName() . ' cancelled their order...');
     }
     }
     

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124. use Symfony\Component\EventDispatcher\EventDispatcher;
     $dispatcher = new EventDispatcher();
     $twitter = new Twitter('demcrookidwigitz', 'b3@tb0Xpr0$');
     // Wire listeners
     $listener = new TwitterListener($twitter);
     $dispatcher->addListener('order.new', array($listener, 'tweetAtOrderer'));
     

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125. use Symfony\Component\EventDispatcher\EventDispatcher;
     $dispatcher = new EventDispatcher();
     $twitter = new Twitter('demcrookidwigitz', 'b3@tb0Xpr0$');
     // Wire listeners
     $listener = new TwitterListener($twitter);
     $dispatcher->addListener('order.new', array($listener, 'tweetAtOrderer'));
     class TwitterListener
     {
     public function __construct(Twitter $twitter) {
     $this->twitter = $twitter;
     }
     public function tweetAtOrderer(CustomerEvent $event) {
     $customer = $event->getOrder();
     $msg = $customer->getTwitterHandle().' Thanks for ordering from us!';
     $this->twitter->tweet($msg);
     }
     }
     

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126. class Controller
     {
     public function __construct(EventDispatcher $dispatcher) {
     $this->dispatcher = $dispatcher;
     }
     public function newCustomer() {
     $customer = new Customer($_POST);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.register', $event);
     }
     public function createOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Created order ' . $number);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.order.new', $event);
     }
     public function cancelOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Cancelled order number ' . $number);
     $eLog = new EmailLogger('boss@demcrookidwigitz.com');
     $eLog->log($customer->getName() . ' cancelled their order...');
     }
     }
     

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127. use Symfony\Component\EventDispatcher\EventDispatcher;
     $dispatcher = new EventDispatcher();
     $bossEmail = 'boss@demcrookidwigitz.com';
     // Wire listeners
     // ...
     $listener = new BossCancelOrderEmailListener(new BossCancelOrderEmail($bossEmail));
     $dispatcher->addListener('customer.order.cancel', array($listener, 'onCancelOrder'));
     class BossCancelOrderEmail
     {
     public function __construct($bossEmail) {
     $this->bossEmail = $bossEmail;
     }
     public function send($name) {
     return mail($this->bossEmail, $this->getSubject(), $this->getMessage($name),
     $this->getHeaders());
     }
     protected function getSubject() {
     return 'Customer Order Cancelled';
     }
     protected function getMessage($name) {
     return "Boss! " . $name . " cancelled their order. Bummer!";
     }
     // ...
     }
     

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128. use Symfony\Component\EventDispatcher\EventDispatcher;
     $dispatcher = new EventDispatcher();
     $bossEmail = 'boss@demcrookidwigitz.com';
     // Wire listeners
     // ...
     $listener = new BossCancelOrderEmailListener(new BossCancelOrderEmail($bossEmail));
     $dispatcher->addListener('customer.order.cancel', array($listener, 'onCancelOrder'));
     class BossCancelOrderEmailListener
     {
     public function __construct(BossCancelOrderEmail $email) {
     $this->email = $email;
     }
     public function onCancelOrder(CustomerEvent $event) {
     $customer = $event->getCustomer();
     $this->email->send($customer->getName());
     }
     }
     

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129. class Controller
     {
     public function __construct(EventDispatcher $dispatcher) {
     $this->dispatcher = $dispatcher;
     }
     public function newCustomer() {
     $customer = new Customer($_POST);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.register', $event);
     }
     public function createOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Created order ' . $number);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.order.new', $event);
     }
     public function cancelOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Cancelled order number ' . $number);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.order.cancel', $event);
     }
     }
     

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130. 1
     0
     Our Second Event
     

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131. class Controller
     {
     public function __construct(EventDispatcher $dispatcher) {
     $this->dispatcher = $dispatcher;
     }
     public function newCustomer() {
     $customer = new Customer($_POST);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.register', $event);
     }
     public function createOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Created order ' . $number);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.order.new', $event);
     }
     public function cancelOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Cancelled order number ' . $number);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.order.cancel', $event);
     }
     }
     

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132. class Controller
     {
     public function __construct(EventDispatcher $dispatcher) {
     $this->dispatcher = $dispatcher;
     }
     public function newCustomer() {
     $customer = new Customer($_POST);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.register', $event);
     }
     public function createOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Created order ' . $number);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.order.new', $event);
     }
     public function cancelOrder() {
     // ...
     $dLog = new DiskLogger('/logs/prod.log');
     $dLog->log('Cancelled order number ' . $number);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.order.cancel', $event);
     }
     }
     class Controller
     {
     public function __construct(EventDispatcher $dispatcher) {
     $this->dispatcher = $dispatcher;
     }
     public function newCustomer() {
     $customer = new Customer($_POST);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.register', $event);
     }
     public function createOrder() {
     // ...
     $event = new OrderEvent($order);
     $this->dispatcher->dispatch('order.new', $event);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.order.new', $event);
     }
     public function cancelOrder() {
     // ...
     $event = new OrderEvent($order);
     $this->dispatcher->dispatch('order.cancel', $event);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.order.cancel', $event);
     }
     }
     

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133. use Symfony\Component\EventDispatcher\Event;
     class OrderEvent extends Event
     {
     protected $order;
     public function __construct(Order $order) {
     $this->order = $order;
     }
     public function getOrder() {
     return $this->order;
     }
     }
     

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134. use Symfony\Component\EventDispatcher\EventDispatcher;
     $dispatcher = new EventDispatcher();
     $diskLogger = new DiskLogger('/logs/prod.log');
     // Wire listeners
     $listener = new OrderLoggerListener($diskLogger);
     $dispatcher->addListener('order.new', array($listener, 'onNewOrder'));
     class OrderLoggerListener
     {
     public function __construct(DiskLogger $logger) {
     $this->logger = $logger;
     }
     public function onNewOrder(OrderEvent $event) {
     $order = $event->getOrder();
     $this->logger->log('Created order number ' . $order->getNumber());
     }
     }
     

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135. use Symfony\Component\EventDispatcher\EventDispatcher;
     $dispatcher = new EventDispatcher();
     $diskLogger = new DiskLogger('/logs/prod.log');
     // Wire listeners
     $listener = new OrderLoggerListener($diskLogger);
     $dispatcher->addListener('order.new', array($listener, 'onNewOrder'));
     $dispatcher->addListener('order.cancel', array($listener, 'onCancelOrder'));
     class OrderLoggerListener
     {
     public function __construct(DiskLogger $logger) {
     $this->logger = $logger;
     }
     public function onNewOrder(OrderEvent $event) {
     $order = $event->getOrder();
     $this->logger->log('Created order number ' . $order->getNumber());
     }
     public function onCancelOrder(OrderEvent $event) {
     $order = $event->getOrder();
     $this->logger->log('Cancelled order number ' . $order->getNumber());
     }
     }
     

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136. class Controller
     {
     public function __construct(EventDispatcher $dispatcher) {
     $this->dispatcher = $dispatcher;
     }
     public function newCustomer() {
     $customer = new Customer($_POST);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.register', $event);
     }
     public function createOrder() {
     // ...
     $event = new OrderEvent($order);
     $this->dispatcher->dispatch('order.new', $event);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.order.new', $event);
     }
     public function cancelOrder() {
     // ...
     $event = new OrderEvent($order);
     $this->dispatcher->dispatch('order.cancel', $event);
     $event = new CustomerEvent($customer);
     $this->dispatcher->dispatch('customer.order.cancel', $event);
     }
     }
     FINISH
     

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137. use Symfony\Component\EventDispatcher\EventDispatcher;
     $dispatcher = new EventDispatcher();
     $diskLogger = new DiskLogger('/logs/prod.log');
     $twitter = new Twitter('demcrookidwigitz', 'b3@tb0Xpr0$');
     $bossEmail = 'boss@demcrookidwigitz.com';
     // Wire listeners
     $listener = new CustomerEmailListener(new WelcomeEmail());
     $dispatcher->addListener('customer.register', array($listener, 'onRegister'));
     $listener = new BossNewCustomerEmailListener(new BossNewCustomerEmail($bossEmail));
     $dispatcher->addListener('customer.register', array($listener, 'onCustomerRegister'));
     $listener = new BossCancelOrderEmailListener(new BossCancelOrderEmail($bossEmail));
     $dispatcher->addListener('customer.order.cancel', array($listener, 'onCancelOrder'));
     $listener = new OrderLoggerListener($diskLogger);
     $dispatcher->addListener('order.new', array($listener, 'onNewOrder'));
     $dispatcher->addListener('order.cancel', array($listener, 'onCancelOrder'));
     $listener = new TwitterListener($twitter);
     $dispatcher->addListener('order.new', array($listener, 'tweetAtOrderer'));
     FINISH
     

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138. Caveats
     

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139. Listeners are notified
     in the order registered
     

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140. Caveat - Priority
     use Symfony\Component\EventDispatcher\EventDispatcher;
     $dispatcher = new EventDispatcher();
     $dispatcher->addListener('customer.register', function(CustomerEvent $event) {
     // First
     });
     $dispatcher->addListener('customer.register', function(CustomerEvent $event) {
     // Second
     });
     $customer = new Customer();
     $customer->setEmail('mikesmith@gmail.com');
     $event = new CustomerEvent($customer);
     $dispatcher->dispatch('customer.register', $event);
     First
     Second
     

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141. unless
     a Priority integer
     is given when
     registering a listener
     

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142. Caveat - Priority
     use Symfony\Component\EventDispatcher\EventDispatcher;
     $dispatcher = new EventDispatcher();
     $dispatcher->addListener('customer.register', function(CustomerEvent $event) {
     // Second
     }, 100);
     $dispatcher->addListener('customer.register', function(CustomerEvent $event) {
     // First
     }, 200);
     $customer = new Customer();
     $customer->setEmail('mikesmith@gmail.com');
     $event = new CustomerEvent($customer);
     $dispatcher->dispatch('customer.register', $event);
     First
     Second
     

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143. Caveat - Priority
     use Symfony\Component\EventDispatcher\EventDispatcher;
     $dispatcher = new EventDispatcher();
     $dispatcher->addListener('customer.register', function(CustomerEvent $event) {
     // Third
     }, 100);
     $dispatcher->addListener('customer.register', function(CustomerEvent $event) {
     // First
     }, 200);
     $dispatcher->addListener('customer.register', function(CustomerEvent $event) {
     // Second
     }, 200);
     $customer = new Customer();
     $customer->setEmail('mikesmith@gmail.com');
     $event = new CustomerEvent($customer);
     $dispatcher->dispatch('customer.register', $event);
     First
     Third
     Second
     

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144. Don’t rely on priority
     

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145. Objects attached to
     Events are passed
     by reference
     

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146. which may lead to
     side effects
     if you’re not careful
     

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147. Caveat - Side Effects
     use Symfony\Component\EventDispatcher\EventDispatcher;
     $dispatcher = new EventDispatcher();
     $dispatcher->addListener('customer.register', function(CustomerEvent $event) {
     echo $event->getCustomer()->getEmail(); // mikesmith@gmail.com
     $event->getCustomer()->setEmail('changed@gmail.com');
     });
     $dispatcher->addListener('customer.register', function(CustomerEvent $event) {
     echo $event->getCustomer()->getEmail(); // changed@gmail.com
     });
     $customer = new Customer();
     $customer->setEmail('mikesmith@gmail.com');
     $event = new CustomerEvent($customer);
     $dispatcher->dispatch('customer.register', $event);
     1. Set Email
     2. Get Email
     3. Update Email
     4. Email not the same
     

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148. Can make
     debugging
     difficult
     

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149. Just ask a
     developer
     

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150. Just ask a
     developer
     

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151. Adobe Desktop Application Codebase
     Source: http://stlab.adobe.com/wiki/index.php/File:2008_07_25_google.pdf
     Event Handling logic
     All other logic
     33%
     Event Handling bugs
     All other bugs
     50%
     

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152. Ideas for Utilizing
     Events
     

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153. Ideas for Utilizing Events
     • Logging
     • Offloading expensive operations to a message queue
     • Email, PDF generation, file system access
     • Setting “created_at” or “updated_at” on an entity
     • Updating a search index when persisting an entity
     • Allowing users of your plug-ins to extend their
     functionality without modifying your code
     • What ideas have you come up with?
     

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154. Further Reading
     • Introduction to Symfony2 EventDispatcher
     http://bit.ly/sf2-event-dispatcher
     • An Introduction to Zend Framework 2 Event Manager
     http://bit.ly/zf2-event-manater
     • The S.O.L.I.D. Principles of OO and Agile Design
     http://bit.ly/uncle-bob-oo-insights
     

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155. Sources
     • http://lampwww.epfl.ch/~imaier/pub/DeprecatingObserversTR2010.pdf
     • http://stlab.adobe.com/wiki/index.php/File:2008_07_25_google.pdf
     Photo Credits
     • http://www.flickr.com/photos/pedromourapinheiro/2456410959/
     • http://www.flickr.com/photos/seat850/3893504473/
     • http://www.flickr.com/photos/slworking/5170065748/
     • http://www.flickr.com/photos/33037982@N04/3727397261/
     • http://www.flickr.com/photos/factoryjoe/26967479/
     

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156. John Kary
     johnkary@
     gmail.com
     @
     johnkary
     Slides @ http://johnkary.net/talks
     WRITING EXTENSIBLE CODE
     USING EVENT DISPATCHER
     https://joind.in/7551
     

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