IoC container - LaravelLive UK 2018

Did you know your IoC container can do a whole lot more than just constructor injection? Besides that it is actually packed with features. Inflectors, resolving callbacks, aliasing, method invocation to name a few. In this talk you will learn how to leverage the power of a great container and service providers to write better, loosely coupled code. Well designed code put together by your IoC container will make your applications SOLID, modular, lean and decoupled from the framework!

Transcript

1. IOC container
   @hannesvdvreken
   @laravelliveuk
   

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2. Hi, my name is Hannes.
   

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3. !
   

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4. IoC Container
   

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5. I
   O
   C
   

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6. International
   O
   C
   

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7. International
   Olympic
   C
   

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8. International
   Olympic
   Committee
   

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9. International
   Olympic
   Committee
   

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10. IoC Container
    

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11. IoC Container
    

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12. WHAT IS IOC?
    IoC == Inversion of Control
    

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13. WHAT IS IOC?
    class Service
    {
    public function __construct()
    {
    init();
    }
    public function init()
    {
    $config = config(‘ftpsettings…’);
    $this->ftp = new FTP(…);
    }
    public function calculate();
    }
    

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14. WHAT IS IOC?
    $service = $container->get(Service::class);
    $service->calculate();
    

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15. But first:
    Design patterns
    WHAT IS IOC?
    

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16. class Service
    {
    public function init()
    { // setup FTP
    }
    public function calculate()
    {
    // Get stuff from FTP.
    // Do calculations.
    // Return result.
    }
    }
    WHAT IS IOC?
    

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17. class Service
    {
    public function __construct(Ftp $ftp)
    {
    }
    public function calculate()
    {
    // Get stuff from FTP.
    // Do calculations.
    // Return result.
    }
    }
    WHAT IS IOC?
    

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18. class Service
    {
    public function __construct(Ftp $ftp)
    {
    }
    public function calculate()
    {
    // Get stuff from FTP.
    // Add caching to prevent hitting FTP over and over again
    // Do calculations.
    // Return result.
    }
    }
    WHAT IS IOC?
    

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19. class Service
    {
    public function __construct(Ftp $ftp)
    {
    }
    public function calculate()
    {
    // Get stuff from FTP.
    // Add caching to prevent hitting FTP over and over again
    // Log that FTP is accessed.
    // Do calculations.
    // Return result.
    }
    }
    WHAT IS IOC?
    

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20. class Service
    {
    public function __construct(Ftp $ftp)
    {
    }
    public function calculate()
    {
    // Get stuff from FTP.
    // Add caching to prevent hitting FTP over and over again
    // Log that FTP is accessed.
    // Do calculations.
    // Return result.
    }
    }
    WHAT IS IOC?
    

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21. class FtpStorage
    {
    public function __construct(Ftp $ftp)
    {
    $this->ftp = $ftp;
    }
    public function get($key)
    {
    // Get it.
    // Cache it.
    // Log it.
    // Return it.
    }
    }
    WHAT IS IOC?
    

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22. class Service
    {
    public function __construct(FtpStorage $storage)
    {

    $this->storage = $storage;
    }
    public function calculate()
    {
    $value = $this->storage->get($key);
    return $calculate($value);
    }
    }
    WHAT IS IOC?
    

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23. interface Storage
    {
    public function get($key);
    }
    WHAT IS IOC?
    

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24. class FtpStorage implements Storage
    {
    public function __construct(Ftp $ftp)
    {
    $this->ftp = $ftp;
    }
    public function get($key)
    {
    …
    }
    }
    WHAT IS IOC?
    

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25. class Service
    {
    public function __construct(Storage $storage)
    {

    $this->storage = $storage;
    }
    }
    WHAT IS IOC?
    

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26. class CacheDecorator implements Storage
    {
    public function __construct(Cache $cache, Storage $wrapped)
    {…}
    public function get($key)
    {
    return $this->cache->remember($key, 60, function () {
    return $this->wrapped->get($key);
    });
    }
    }
    WHAT IS IOC?
    

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27. class LogDecorator implements Storage
    {
    public function __construct(LoggerInterface $log, Storage $wrapped)
    {…}
    public function get($key)
    {
    $this->log->info('Retrieved value for '.$key);
    return $this->wrapped->get($key);
    }
    }
    WHAT IS IOC?
    

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28. class FtpStorage implements Storage
    {
    public function __construct(Ftp $ftp)
    {
    $this->ftp = $ftp;
    }
    public function get($key)
    {
    // Get it and return it.
    }
    }
    WHAT IS IOC?
    

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29. FtpStorage
    Service
    depends on
    depends on
    Ftp
    WHAT IS IOC?
    

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30. FtpStorage
    implements
    Storage
    Service
    depends on
    depends on
    Ftp
    WHAT IS IOC?
    

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31. FtpStorage
    Storage
    CacheDecorator
    Service
    LogDecorator
    S3Storage
    WHAT IS IOC?
    implements
    depends on
    

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32. WHAT IS IOC?
    FtpStorage
    implements
    Storage
    Service
    depends on
    depends on
    Ftp
    FtpStorage
    ervice
    depends on
    depends on
    Ftp
    

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33. new Service($ftp);
    WHAT IS IOC?
    

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34. new Service(
    new CacheDecorator(
    $cache,
    new LogDecorator(
    $logger,
    new FtpStorage(
    new Ftp($settings)
    )
    )
    )
    );
    WHAT IS IOC?
    

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35. $container->get(Service::class);
    1) Make FtpStorage
    2) Wrap it with LogDecorator
    3) Wrap LogDecorator instance with CacheDecorator
    4) New up Service with CacheDecorator instance.
    WHAT IS IOC?
    

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36. Dependency inversion:
    Interface + implementation
    Dependency injection:
    Injecting `Storage` into `Service`
    Inversion of Control:
    The container builds your objects and calls them
    WHAT IS IOC?
    

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37. Inversion of Control
    IoC container to the rescue
    WHAT IS IOC?
    

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38. Let the IoC container help
    you with Composition
    WHAT IS IOC?
    

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39. symfony/dependency-injection
    illuminate/container
    aura/di
    zendframework/zend-di
    pimple/pimple
    league/container
    bitexpert/disco
    …
    container-interop/container-interop
    psr/container (PSR-11)
    CONSTRUCTOR INJECTION
    

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40. PSR-11
    namespace Psr\Container;
    interface ContainerInterface
    {
    public function get($id);
    public function has($id);
    }
    

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44. Automatic object resolution
    

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45. $listener = $container->get(SendInvoice::class);
    $listener->listen($event);
    CONSTRUCTOR INJECTION
    

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46. Reflection
    CONSTRUCTOR INJECTION
    

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47. class SendInvoice
    {
    public function __construct(Mailer $mailer)
    {
    $this->mailer = $mailer;
    }
    public function listen(InvoiceGeneratedEvent $event)
    {
    …
    }
    }
    CONSTRUCTOR INJECTION
    

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48. Constructor injection
    CONSTRUCTOR INJECTION
    

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49. (new \ReflectionClass($classname))
    ->getConstructor()
    ->getParameters();
    CONSTRUCTOR INJECTION
    

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50. Recursively
    CONSTRUCTOR INJECTION
    

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51. CONSTRUCTOR INJECTION
    SendInvoice ➡ Mailer ➡ SMTP
    

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52. Auto wiring:
    - Laravel
    - Symfony
    - Zend
    - league/container
    - …
    CONSTRUCTOR INJECTION
    

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53. But what if our code is SOLID…
    The container can’t construct
    interfaces?
    CONSTRUCTOR INJECTION
    

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54. Helping the container
    

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55. $container->bind($key, $closure);
    REGISTRATION - BINDING
    

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56. $container->bind(Mailer::class, function () {
    // Create mailer…
    return $mailer;
    });
    REGISTRATION - BINDING
    

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57. Situation 1:
    When <> is type hinted,
    resolve <> instead
    REGISTRATION - BINDING
    

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58. Solution:
    Aliasing.
    REGISTRATION - BINDING
    

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59. $container->alias(MailerInterface::class, Mailer::class);
    REGISTRATION - BINDING
    

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60. $container->bind(MailerInterface::class, function () {
    return $container->get(Mailer::class);
    });
    REGISTRATION - BINDING
    

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61. Situation 2:
    When <> has non-type hinted
    constructor arguments.
    REGISTRATION - BINDING
    

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62. Solution:
    Define explicitly.
    REGISTRATION - BINDING
    

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63. $container->bind(Mailer::class, function () {
    return new Mailer($username, $password);
    });
    REGISTRATION - BINDING
    

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64. // Symfony
    $container->register(Mailer::class)
    ->addArgument($username)
    ->addArgument($password);
    REGISTRATION - BINDING
    

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65. Situation 3:
    When <> is type hinted,
    always return the exact same object.
    REGISTRATION - BINDING
    

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66. Example:
    Global state in a
    - Translator (user’s locale)
    - Entity Manager
    - Event dispatcher
    REGISTRATION - BINDING
    

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67. Solution:
    Sharing an instance.
    REGISTRATION - BINDING
    

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68. $container->singleton(EntityManagerInterface::class, function ()
    …
    });
    $container->bind($key, $function, true);
    REGISTRATION - BINDING
    

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69. Situation 4:
    When different classes need a
    different object of the same
    interface.
    REGISTRATION - BINDING
    

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70. class PhotosController
    {
    public function __construct(FilesystemInterface $photos)
    {
    }
    }
    class FilesController
    {
    public function __construct(FilesystemInterface $files)
    {
    }
    }
    REGISTRATION - BINDING
    

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71. Solution:
    Contextual binding.
    REGISTRATION - BINDING
    

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72. $container
    ->when(PhotosController::class)
    ->needs(FilesystemInterface::class)
    ->give(‘fs.photos');
    $container->bind('fs.photos', function () {});
    $container->bind('fs.files', function () {});
    REGISTRATION - CONTEXTUAL BINDING
    

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73. $container->bind('fs.photos', …);
    $container->bind(PhotosController::class, function
    $fs = $container->get('fs.photos');
    return new PhotosController($fs);
    });
    REGISTRATION - BINDING
    

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74. Situation 5:
    When resolving <>, do
    some setup.
    REGISTRATION - BINDING
    

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75. Example 1:
    When resolving the EntityManager,
    register some ModelListeners.
    REGISTRATION - BINDING
    

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76. Example 2:
    interface EnvironmentAware
    {
    public function setEnv($env);
    }
    trait EnvironmentAware
    {
    public function setEnv($env)
    {
    $this->env = $env;
    }
    }
    REGISTRATION - CONTAINER EVENTS
    

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77. Solution:
    Container events / inflection / hooks / …
    REGISTRATION - BINDING
    

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78. $container->resolving(function (EnvironmentAware $object) {
    $object->setEnv(app()->environment());
    });
    REGISTRATION - CONTAINER EVENTS
    

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79. Also useful for:
    - Quickly injecting stuff
    REGISTRATION - CONTAINER EVENTS
    

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80. interface CommandBusAware
    trait CommandBusAware
    interface EventDispatcherAware
    trait EventDispatcherAware
    REGISTRATION - CONTAINER EVENTS
    

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81. Also useful for:
    - Quickly injecting stuff
    REGISTRATION - CONTAINER EVENTS
    

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82. Also useful for:
    - Quickly injecting stuff
    - Injecting soft dependencies
    REGISTRATION - CONTAINER EVENTS
    

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83. $container—>resolving(function (Mailer $mailer) {
    $mailer->setQueueResolver(function () {
    return $container->get(Queue::class);
    });
    );
    REGISTRATION - CONTAINER EVENTS
    

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85. Also useful for:
    - Quickly injecting stuff
    - Injecting soft dependencies
    REGISTRATION - CONTAINER EVENTS
    

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86. Also useful for:
    - Quickly injecting stuff
    - Injecting soft dependencies
    - Setting configurable values
    REGISTRATION - CONTAINER EVENTS
    

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87. $container->resolving(function (Validator $validator) {
    $fileTypes = $container->get('config')->get(…)
    $validator->setAllowedFileTypes($fileTypes);
    );
    REGISTRATION - CONTAINER EVENTS
    

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88. Where to put all this?
    REGISTRATION
    

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89. Service Providers!
    REGISTRATION
    

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90. REGISTRATION
    public function boot()
    {
    // Macros, extensions, container events, …
    }
    public function register()
    {
    // Bindings
    }
    

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91. REGISTRATION
    public function boot(View $view)
    {
    $view->composer(…);
    }
    

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92. REGISTRATION
    protected $defer = true;
    public function provides()
    {
    return [Connection::class];
    }
    public function register()
    {
    $this->app->bind(Connection::class, …);
    }
    

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93. Using a container
    

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94. Retrieving objects
    CALLING THE CONTAINER
    

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95. // Psr\Container\ContainerInterface
    $container->has('fs');
    $container->get('fs');
    CALLING THE CONTAINER
    

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96. Retrieving objects, with arguments
    CALLING THE CONTAINER
    

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97. $container->bind(‘fs', function ($args) {
    // Use $args[0] to see what folder to use.
    });
    $container->get('fs', [‘images']);
    CALLING THE CONTAINER
    

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98. $container->bind(‘fs', function ($args) {
    // Use $args[0] to see what folder to use.
    });
    $container->get('fs', [‘images']);
    $container->bind('fs.images', function () {
    return $container->get('fs', ['images']);
    });
    CALLING THE CONTAINER
    

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99. Calling functions, with resolved params
    CALLING THE CONTAINER
    

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100. $container->call($closure);
     $container->call(function (Mailer $mailer) {});
     $container->call([$listener, 'handle']);
     $container->call(‘Listener::handle’);
     CALLING THE CONTAINER
     

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101. $container->call($closure);
     $container->call(function (Mailer $mailer) {});
     $container->call([$listener, 'handle']);
     $container->call(‘Listener::handle’);
     $container->call(‘Listener@handle');
     CALLING THE CONTAINER
     

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102. (new ReflectionFunction($callback))
     ->getParameters();
     CALLING THE CONTAINER
     

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103. $func = $container->wrap('Listener@handle');
     $func();
     CALLING THE CONTAINER
     

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104. public function wrap($callback) {
     return function () {
     return $this->call($callback);
     };
     }
     CALLING THE CONTAINER
     

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105. Tagging
     CALLING THE CONTAINER
     

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106. $container->tag('fs.images', 'filesystem');
     $container->tag('fs.pdfs', 'filesystem');
     $filesystems = $container->tagged('filesystem');
     foreach ($filesystems as $filesystem) {
     …
     }
     CALLING THE CONTAINER
     

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107. $container->tag(‘tool-1.dispatcher’, 'dispatcher');
     $container->tag(‘tool-2.dispatcher’, 'dispatcher');
     $dispatchers = $container->tagged(‘dispatcher');
     foreach ($dispatchers as $dispatcher) {
     $listener->delegate($dispatcher);
     }
     CALLING THE CONTAINER
     

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108. When to inject the container?
     

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109. Preferably only in
     - Event Dispatchers
     - Router
     - Command Bus
     - Factories
     - …
     CALLING THE CONTAINER
     

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110. Bonus
     

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111. Solving circular
     dependencies
     BONUS - CIRCULAR DEPENDENCIES
     

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112. $mailer = new Mailer(QueueInterface $queue);
     $queue = new Queue(MailerInterface $mailer);
     BONUS - CIRCULAR DEPENDENCIES
     

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113. $mailer = new Mailer();
     $queue = new Queue(MailerInterface $mailer);
     $mailer->setQueueResolver($callable);
     BONUS - CIRCULAR DEPENDENCIES
     

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114. $queue = $container->get(QueueInterface::class);
     $container->resolving(function (Mailer $mailer) {
     $mailer->setQueueResolver(function () {
     return $container->get(QueueInterface::class);
     });
     });
     BONUS - CIRCULAR DEPENDENCIES
     

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115. Environment aware injection
     $container->bind(‘fs.photos’, function () {
     if (getenv(‘APP_ENV’) === ‘integration’) {
     // Fill in memory adapter
     // with integration testing files

     } else {
     // Normal connection to S3.
     }
     });
     BONUS
     

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116. recap:
     Reflection
     Aliasing
     Soft dependencies
     Using container
     

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117. Thank you!
     @hannesvdvreken
     @laravelliveuk
     

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118. Time for
     questions.
     @hannesvdvreken
     @laravelliveuk
     

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