Separation of concerns - DPC 12

Transcript

1. Separation of Concerns

2. Separation of concerns About Joshua  Joshua Thijssen, NoxLogic /

   Techademy  Freelance Consultant, Developer, Trainer  Development in PHP, Python, Perl, C, Java  [email protected]  @jaytaph

3. Separation of concerns About Stephan  Stephan Hochdörfer, bitExpert AG

    Department Manager Research Labs  enjoying PHP since 1999  [email protected]  @shochdoerfer

4. Separation of concerns It is what I sometimes have called

   the separation of concerns, which [...] is yet the only available technique for effective ordering of one's thoughts. Edsger W. Dijkstra, "On the role of scientific thought" (1974)

5. Separation of concerns SoC […] is the process of breaking

   a computer program into distinct features that overlap in functionality as little as possible. http://en.wikipedia.org/wiki/Separation_of_concerns

6. Separation of concerns It`s all about focusing!

7. Separation of concerns One step a time. Focus on the

   details!

8. Separation of concerns <?php $items = array(); $token = file_get_contents("https://graph.facebook.com/oauth/access_token?...");

   $feed = file_get_contents("https://graph.facebook.com/ident/feed?".$token); $feed = json_decode($feed, true); foreach($feed['data'] as $post) { if('123456789012' === $post['from']['id']) { $items[] = array( 'date' => strtotime($post['created_time']), 'message' => $post['message']); } } $feed = file_get_contents("http://search.twitter.com/search.json?q=from:ident"); $feed = json_decode($feed, true); foreach($feed['results'] as $tweet) { $items[] = array( 'date' => strtotime($tweet['created_at']), 'message' => $tweet['text']); } foreach($items as $item) { echo $item['message']; }

9. Separation of concerns <?php $items = array(); $token = file_get_contents("https://graph.facebook.com/oauth/access_token?...");

   $feed = file_get_contents("https://graph.facebook.com/ident/feed?".$token); $feed = json_decode($feed, true); foreach($feed['data'] as $post) { if('123456789012' === $post['from']['id']) { $items[] = array( 'date' => strtotime($post['created_time']), 'message' => $post['message']); } } $feed = file_get_contents("http://search.twitter.com/search.json?q=from:ident"); $feed = json_decode($feed, true); foreach($feed['results'] as $tweet) { $items[] = array( 'date' => strtotime($tweet['created_at']), 'message' => $tweet['text']); } foreach($items as $item) { echo $item['message']; }} Controller part!

10. Separation of concerns <?php $items = array(); $token = file_get_contents("https://graph.facebook.com/oauth/access_token?...");

    $feed = file_get_contents("https://graph.facebook.com/ident/feed?".$token); $feed = json_decode($feed, true); foreach($feed['data'] as $post) { if('123456789012' === $post['from']['id']) { $items[] = array( 'date' => strtotime($post['created_time']), 'message' => $post['message']); } } $feed = file_get_contents("http://search.twitter.com/search.json?q=from:ident"); $feed = json_decode($feed, true); foreach($feed['results'] as $tweet) { $items[] = array( 'date' => strtotime($tweet['created_at']), 'message' => $tweet['text']); } foreach($items as $item) { echo $item['message']; } View part!

11. Separation of concerns Very unstable. Not safe for changes....

12. Separation of concerns „Make everything as simple as possible...“

13. Separation of concerns Establish boundaries

14. Separation of concerns What are the boundaries? Presentation Layer

15. Separation of concerns What are the boundaries? Presentation Layer Business

    Layer

16. Separation of concerns What are the boundaries? Presentation Layer Business

    Layer Resource Access Layer

17. Isolate functionality, break it apart! Separation of concerns

18. Separation of concerns <?php namespace Acme\DemoBundle\Controller; use Symfony\Bundle\FrameworkBundle\Controller\Controller; use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route;

    use Sensio\Bundle\FrameworkExtraBundle\Configuration\Template; class DemoController extends Controller { /** * @Route("/", name="_demo") * @Template() */ public function indexAction() { $items = array(); $token = file_get_contents("https://graph.facebook.com/oauth/access_to..."); $feed = file_get_contents("https://graph.facebook.com/ident/feed?".$token); $feed = json_decode($feed, true); foreach($feed['data'] as $post) { if('123456789012' === $post['from']['id']) { $items[] = array( 'date' => strtotime($post['created_time']), 'message' => $post['message']); } }

19. Separation of concerns $feed = file_get_contents("http://search.twitter.com/search.json?..."); $feed = json_decode($feed, true);

    foreach($feed['results'] as $tweet) { $items[] = array( 'date' => strtotime($tweet['created_at']), 'message' => $tweet['text']); } return array('items' => $items); } }

20. Focus on one responsibility a time! Separation of concerns

21. Separation of concerns <?php namespace Acme\DemoBundle\Controller; use Symfony\Bundle\FrameworkBundle\Controller\Controller; use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route;

    use Sensio\Bundle\FrameworkExtraBundle\Configuration\Template; class DemoController extends Controller { /** * @Route("/", name="_demo") * @Template() */ public function indexAction() { $items = array(); $token = file_get_contents("https://graph.facebook.com/oauth/access_to..."); $feed = file_get_contents("https://graph.facebook.com/ident/feed?".$token); $feed = json_decode($feed, true); foreach($feed['data'] as $post) { if('123456789012' === $post['from']['id']) { $items[] = array( 'date' => strtotime($post['created_time']), 'message' => $post['message']); } } Facebook connector

22. Separation of concerns $feed = file_get_contents("http://search.twitter.com/search.json?..." ); $feed = json_decode($feed,

    true); foreach($feed['results'] as $tweet) { $items[] = array( 'date' => strtotime($tweet['created_at']), 'message' => $tweet['text']); } return array('items' => $items); } } Twitter connector

23. Interfaces as a contract Separation of concerns

24. Separation of concerns <?php interface ConnectorInterface { /** * Will

    return an array of the latest posts. * return array */ public function getLatestPosts() { } }

25. Separation of concerns <?php class FacebookConnector implements ConnectorInterface { protected

    $handle; public function __construct($handle) { $this->handle = $handle; } public function getLatestPosts() { $items = array(); $token = file_get_contents("https://graph.facebook.com/oauth/access..."); $feed = file_get_contents("https://graph.facebook.com/. $this->handle."/feed?".$token); $feed = json_decode($feed, true); foreach($feed['data'] as $post) { if('123456789012' === $post['from']['id']) { $items[] = array( 'date' => strtotime($post['created_time']), 'message' => $post['message']); } } return $items; } }

26. Separation of concerns <?php class FacebookConnector implements ConnectorInterface { protected

    $handle; public function __construct($handle) { $this->handle = $handle; } public function getLatestPosts() { $token = $this->getAccessToken(); return $this->readPosts($token); } protected function getAccessToken() { return file_get_contents("https://graph.facebook.com/oauth/access_?..."); } protected function readPosts($token) { // read the post, filter all relevant and return them... } }

27. Separation of concerns <?php class FacebookConnectorV2 extends FacebookConnector { protected

    function getAccessToken() { return md5($this->handle); } } Easy to extend, will not influence the behaviour of other methods!

28. Separation of concerns <?php namespace Acme\DemoBundle\Controller; use Symfony\Bundle\FrameworkBundle\Controller\Controller; use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route;

    use Sensio\Bundle\FrameworkExtraBundle\Configuration\Template; class DemoController extends Controller { /** * @Route("/", name="_demo") * @Template() */ public function indexAction() { $items = array(); $fb = $this->get('FbConnector'); $items += $fb->getLatestPosts(); $feed = file_get_contents("http://search.twitter.com/search.json?..."); $feed = json_decode($feed, true); foreach($feed['results'] as $tweet) { $items[] = array( 'date' => strtotime($tweet['created_at']), 'message' => $tweet['text']); }

29. Separation of concerns <?php namespace Acme\DemoBundle\Controller; use Symfony\Bundle\FrameworkBundle\Controller\Controller; use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route;

    use Sensio\Bundle\FrameworkExtraBundle\Configuration\Template; class DemoController extends Controller { /** * @Route("/", name="_demo") * @Template() */ public function indexAction() { $items = array(); $fb = $this->get('FbConnector'); $items += $fb->getLatestPosts(); $twitter = $this->get('TwitterConnector'); $items += $twitter->getLatestPosts(); return array('items' => $items); } }

30. Will improve the testability! Separation of concerns

31. Will reduce tight coupling! Separation of concerns

32. Will increase component reuse! Separation of concerns

33. The value of separation Why should I do it? Separation

    of concerns

34. The value of separation 1. Getting rid of code duplication

    Separation of concerns

35. The value of separation 2. Application becomes more stable and

    easier to understand Separation of concerns

36. The value of separation 3. Single responsibility offers clear extension

    points Separation of concerns

37. The value of separation 4. Increases the reusability of components

    Separation of concerns

38. Separation of concerns How to separate the concerns?

39. Separation of concerns How to separate? Horizontal Separation Presentation Layer

    Business Layer Resource Access Layer

40. Separation of concerns How to separate? Horizontal Separation ./symfony |-app

    |---cache |---config |---Resources |-src |---Acme |-----DemoBundle |-------Controller |-------Resources |---------config |---------public |-----------css |-----------images |---------views |-----------Demo |-----------Welcome |-------Tests |---------Controller |-web

41. Separation of concerns How to separate? Service Separation Service Interface

    Layer Business Layer Resource Access Layer

42. Separation of concerns How to separate? Service Separation Frontend /

    UI Webservers REST API Datastore Solr Search Service

43. Separation of concerns How to separate? Vertical Separation Module A

    Module B Module C

44. Separation of concerns How to separate? Vertical Separation ./symfony |-app

    |---cache |---config |---Resources |-src |---Acme |-----AdminBundle |-------Controller |-------Resources |-------Tests |-----ProductsBundle |-------Controller |-------Resources |-------Tests |-----CustomersBundle |-------Controller |-------Resources |-------Tests |-web

45. Separation of concerns How to separate? Vertical Separation Presentation Layer

    Business Layer Resource Access Layer Presentation Layer Business Layer Resource Access Layer Presentation Layer Business Layer Resource Access Layer

46. Separation of concerns How to separate? Vertical Separation ./symfony |-app

    |---cache |---config |---Resources |-src |---Acme |-----AdminBundle |-------Controller |-------Resources |-------Tests |-----ProductsBundle |-------Controller |-------Resources |-------Tests |-----CustomersBundle |-------Controller |-------Resources |-------Tests |-web

47. Cross-cutting concerns? How to deal with security or logging aspects?

    Separation of concerns

48. Separation of concerns How to separate? Aspect Separation Presentation Layer

    Business Layer Resource Access Layer Aspects

49. Separation of concerns How to separate? Aspect Separation <?php namespace

    Acme\Products\Aspects; /** * @FLOW3\Aspect */ class LoggingAspect { /** * @FLOW3\Inject * @var \Acme\Logger\LoggerInterface */ protected $logger; /** * @param \TYPO3\FLOW3\AOP\JoinPointInterface $joinPoint * @FLOW3\Before("method(Acme\Products\Model\Product->delete())") */ public function log(\TYPO3\FLOW3\AOP\JoinPointInterface $jp) { $product = $jp->getMethodArgument('product'); $this->logger->info('Removing ' . $product->getName()); } }

50. Separation of concerns Dependency Direction

51. Separation of concerns Dependency Direction "High-level modules should not depend

    on low-level modules. Both should depend on abstractions." Robert C. Martin

52. Separation of concerns Inverting Concerns Presentation Layer Business Layer Resource

    Access Layer

53. Separation of concerns Inverting Concerns Presentation Layer Business Layer Resource

    Access Layer Presentation Layer Business Layer Resource Access Layer UI Component

54. Separation of concerns Inverting Concerns The goal of Dependency Injection

    is to separate the concerns of obtaining the dependencies from the core concerns of a component.

55. Separation of concerns What are the benefits? Let`s recap....

56. Separation of concerns What are the benefits? 1. Facilitate reusability

57. Separation of concerns What are the benefits? 2. Ensure the

    maintainability

58. Separation of concerns What are the benefits? 3. Increasing the

    code quality

59. Separation of concerns What are the benefits? 4. Enables everyone

    to understand the application

60. Separation of concerns What are the benefits? 5. Allows developers

    to work on components in isolation

61. Thank you!

62. http://joind.in/6244