Decoupling from the framework

A framework, by definition, provides a basic set of tools for application development we can use to avoid writing repeatable code. It often encourages to take shortcuts to enable rapid development. In theory, we only need to implement the part which is specific to our domain. In practice, we often end up with highly coupled code, mixed layers and a dependency graph deceptively close to spaghetti.
Jakub will take Symfony as an example to present techniques of decoupling from a framework and keeping it on a distance.

Transcript

1. Decoupling from the framework Jakub Zalas 7th of April 2014
2. @jakzal @jakub_zalas @SensioLabsUK £  
3. COUPLING
4. "MODULES ARE COUPLED IF CHANGING ONE OF THEM REQUIRES CHANGING ANOTHER ONE." http://martinfowler.com/ieeeSoftware/coupling.pdf Martin Fowler
5. tight coupling loose coupling
6. COUPLING AND COHESION
7. tight coupling low cohesion
8. loose coupling high cohesion
9. WHY IS TIGHT COUPLING BAD?
10. WHY IS LOOSE COUPLING GOOD?
11. REUSABILITY
12. READABILITY
13. MAINTENANCE
14. CHANGE
15. LOOSEN UP? How to
16. MAKE DEPENDENCIES EXPLICIT
17. class PackageCrawler { public function crawl($resource) { $browser = Browser::getInstance(); $response = $browser->get($resource); // @todo parse } }
18. use Buzz\Browser; class PackageCrawler { public function crawl($resource) { $browser = new Browser(); $response = $browser->get($resource); // @todo parse } }
19. DEPENDENCY INJECTION !
20. use Buzz\Browser; class PackageCrawler { private $browser; public function __construct(Browser $browser) { $this->browser = $browser; } public function crawl($resource) { $response = $this->browser->get($resource); // @todo parse } }
21. INJECT EXACTLY WHAT YOU NEED
22. use Buzz\Browser; class PackageCrawler { private $browser; public function __construct(Browser $browser) { $this->browser = $browser; } public function crawl($resource, Container $container) { $user = $container->get('security.context') ->getToken()->getUser(); $response = $this->browser->get( $resource, array('X-User' => $user->getId()) ); // @todo parse } }
23. https://twitter.com/iamtankist/status/359382451816112129
24. use Buzz\Browser; class PackageCrawler { private $browser; public function __construct(Browser $browser) { $this->browser = $browser; } public function crawl($resource, $userId) { $response = $this->browser->get( $resource, array('X-User' => $userId) ); // @todo parse } }
25. DON'T MIX LAYERS
26. use Buzz\Browser; use Symfony\Component\Console\Input\InputInterface; class PackageCrawler { private $browser; public function __construct(Browser $browser) { $this->browser = $browser; } public function crawl(InputInterface $input) { $response = $this->browser->get( $input->getOption('resource') ); // @todo parse } }
27. use Buzz\Browser; class PackageCrawler { private $browser; public function __construct(Browser $browser) { $this->browser = $browser; } public function crawl($resource) { $response = $this->browser->get( $resource ); // @todo parse } }
28. BI-DIRECTIONAL DEPENDENCIES ARE A SMELL
29. BREAK DEPENDENCIES
30. use Buzz\Browser; class PackageCrawler { private $browser; public function __construct(Browser $browser) { $this->browser = $browser; } public function crawl($resource) { $response = $this->browser->get($resource); // @todo parse } }
33. interface HttpClient { public function get($resource, array $headers = []); }
34. class PackageCrawler { private $httpClient; public function __construct(HttpClient $httpClient) { $this->httpClient = $httpClient; } public function crawl($resource) { $response = $this->httpClient->get($resource); // @todo parse } }
37. use Buzz\Browser; class BuzzClient implements HttpClient { private $browser; public function __construct(Browser $browser) { $this->browser = $browser; } public function get($resource, array $headers) { return (string) $this->browser->get( $resource, $headers ); } }
38. use Guzzle\Client; class GuzzleClient implements HttpClient { private $guzzle; public function __construct(Client $guzzle) { $this->guzzle = $guzzle; } public function get($resource, array $headers) { $request = $this->guzzle->createRequest( 'GET', $resource ); $response = $request->send(); return $response->getBody(); } }
39. DEFER DECISIONS
40. DEFER COMMITMENT
41. FRAMEWORK?
42. use Symfony\Bundle\FrameworkBundle\Controller\Controller; class SearchController extends Controller { public function searchAction(Request $request) { $keywords = $request->query->get('keywords'); $products = $this->getDoctrine() ->getRepository('Acme:Product') ->search($keywords); return $this->render( 'template.html.twig', array('products' => $products) ); } }
43. LAYERED ARCHITECTURE
44. https://www.goodreads.com/book/show/179133.Domain_driven_Design
45. CLEAN ARCHITECTURE
46. http://blog.8thlight.com/uncle-bob/2012/08/13/the-clean-architecture.html
47. SOURCE CODE DEPENDENCIES CAN ONLY POINT INWARDS
48. HEXAGONAL ARCHITECTURE a.k.a. PORTS AND ADAPTERS
49. Application Doctrine In memory UI Tests CLI
50. "Create your application to work without either a UI or a database […]" http://alistair.cockburn.us/Hexagonal+architecture
51. UI IS AN IMPLEMENTATION DETAIL
52. DATABASE IS AN IMPLEMENTATION DETAIL
53. FRAMEWORK IS AN IMPLEMENTATION DETAIL
55. STEP 0 MAKE DEPENDENCIES EXPLICIT
56. use Doctrine\Common\Persistence\ManagerRegistry; use Symfony\Bundle\FrameworkBundle\Templating\EngineInterface; class SearchController { private $templating; private $doctrine; public function __construct( EngineInterface $templating, ManagerRegistry $doctrine ) { $this->templating = $templating; $this->doctrine = $doctrine; } }
57. // .. class SearchController { // ... public function searchAction(Request $request) { $keywords = $request->query->get('keywords'); $repository = $this->doctrine ->getRepository('Acme:Product') ->search($keywords); return $this->templating->renderResponse( 'template.html.twig', array('products' => $products) ); } }
58. STEP 1 ONLY INJECT WHAT YOU ACTUALLY NEED
59. use Doctrine\Common\Persistence\ManagerRegistry; use Symfony\Bundle\FrameworkBundle\Templating\EngineInterface; class SearchController { private $templating; private $doctrine; public function __construct( EngineInterface $templating, ManagerRegistry $doctrine ) { $this->templating = $templating; $this->doctrine = $doctrine; } }
60. use Acme\ProductBundle\Entity\ProductRepository; use Symfony\Bundle\FrameworkBundle\Templating\EngineInterface; class SearchController { private $templating; private $repository; public function __construct( EngineInterface $templating, ProductRepository $repository ) { $this->templating = $templating; $this->repository = $repository; } }
61. // .. class SearchController { // ... public function searchAction(Request $request) { $keywords = $request->query->get('keywords'); $repository = $this->repository->search($keywords); return $this->templating->renderResponse( 'template.html.twig', array('products' => $products) ); } }
62. STEP 2 DON'T TALK TO THE INFRASTRUCTURE DIRECTLY
63. namespace Acme\ProductCatalog; interface ProductRepository { /** * @param string $keywords * * @return Product[] */ public function search($keywords); }
64. use Acme\ProductCatalog\ProductRepository; use Symfony\Bundle\FrameworkBundle\Templating\EngineInterface; class SearchController { private $templating; private $repository; public function __construct( EngineInterface $templating, ProductRepository $repository ) { $this->templating = $templating; $this->repository = $repository; } }
66. DON'T FOLLOW THE FRAMEWORK
67. $this->getDoctrine() ->getRepository('Acme:product') ->find($keywords);
68. MAKE IT OPTIONAL
69. A GOOD FRAMEWORK WILL HELP YOU
70. $this->repository->search($keywords); <service id="acme_product.search_repo" class="Acme\ProductCatalog\ProductRepository" factory-service="doctrine" factory-method="getRepository"> <argument>Acme:Product</argument> </service>
71. DON'T START WITH THE FRAMEWORK
72. MAKE YOUR APPLICATION INDEPENDENT
73. AND THEN INTEGRATE IT WITH THE FRAMEWORK
74. REMEMBER!
75. TDD IS YOUR FRIEND
76. THANK YOU!
77. Credits