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
   

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2. @jakzal
   @jakub_zalas
   @SensioLabsUK
   £  
   

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3. COUPLING
   

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4. "MODULES ARE COUPLED
   IF CHANGING ONE OF THEM
   REQUIRES CHANGING ANOTHER
   ONE."
   http://martinfowler.com/ieeeSoftware/coupling.pdf
   Martin Fowler
   

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5. tight
   coupling
   loose
   coupling
   

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6. COUPLING AND COHESION
   

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7. tight
   coupling
   low
   cohesion
   

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8. loose
   coupling
   high
   cohesion
   

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9. WHY IS
   TIGHT
   COUPLING
   BAD?
   

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10. WHY IS
    LOOSE
    COUPLING
    GOOD?
    

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11. REUSABILITY
    

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12. READABILITY
    

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13. MAINTENANCE
    

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14. CHANGE
    

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15. LOOSEN UP?
    How to
    

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16. MAKE
    DEPENDENCIES
    EXPLICIT
    

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17. class PackageCrawler
    {
    public function crawl($resource)
    {
    $browser = Browser::getInstance();
    $response = $browser->get($resource);
    // @todo parse
    }
    }
    

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18. use Buzz\Browser;
    class PackageCrawler
    {
    public function crawl($resource)
    {
    $browser = new Browser();
    $response = $browser->get($resource);
    // @todo parse
    }
    }
    

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19. DEPENDENCY
    INJECTION !
    

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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
    }
    }
    

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21. INJECT
    EXACTLY
    WHAT YOU
    NEED
    

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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
    }
    }
    

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23. https://twitter.com/iamtankist/status/359382451816112129
    

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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
    }
    }
    

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25. DON'T MIX
    LAYERS
    

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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
    }
    }
    

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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
    }
    }
    

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28. BI-DIRECTIONAL
    DEPENDENCIES
    ARE A SMELL
    

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29. BREAK
    DEPENDENCIES
    

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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
    }
    }
    

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33. interface HttpClient
    {
    public function get($resource, array $headers = []);
    }
    

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34. class PackageCrawler
    {
    private $httpClient;
    public function __construct(HttpClient $httpClient)
    {
    $this->httpClient = $httpClient;
    }
    public function crawl($resource)
    {
    $response = $this->httpClient->get($resource);
    // @todo parse
    }
    }
    

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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
    );
    }
    }
    

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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();
    }
    }
    

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39. DEFER
    DECISIONS
    

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40. DEFER
    COMMITMENT
    

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41. FRAMEWORK?
    

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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)
    );
    }
    }
    

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43. LAYERED
    ARCHITECTURE
    

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44. https://www.goodreads.com/book/show/179133.Domain_driven_Design
    

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45. CLEAN
    ARCHITECTURE
    

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46. http://blog.8thlight.com/uncle-bob/2012/08/13/the-clean-architecture.html
    

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47. SOURCE CODE
    DEPENDENCIES
    CAN ONLY POINT
    INWARDS
    

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48. HEXAGONAL
    ARCHITECTURE
    a.k.a.
    PORTS AND
    ADAPTERS
    

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49. Application
    Doctrine
    In
    memory
    UI
    Tests
    CLI
    

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50. "Create your application to
    work without either a
    UI or a database
    […]"
    http://alistair.cockburn.us/Hexagonal+architecture
    

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51. UI
    IS AN
    IMPLEMENTATION
    DETAIL
    

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52. DATABASE
    IS AN
    IMPLEMENTATION
    DETAIL
    

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53. FRAMEWORK
    IS AN
    IMPLEMENTATION
    DETAIL
    

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55. STEP 0
    MAKE
    DEPENDENCIES
    EXPLICIT
    

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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;
    }
    }
    

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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)
    );
    }
    }
    

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58. STEP 1
    ONLY INJECT WHAT
    YOU ACTUALLY
    NEED
    

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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;
    }
    }
    

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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;
    }
    }
    

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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)
    );
    }
    }
    

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62. STEP 2
    DON'T TALK TO THE
    INFRASTRUCTURE
    DIRECTLY
    

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63. namespace Acme\ProductCatalog;
    interface ProductRepository
    {
    /**
    * @param string $keywords
    *
    * @return Product[]
    */
    public function search($keywords);
    }
    

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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;
    }
    }
    

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66. DON'T FOLLOW
    THE FRAMEWORK
    

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67. $this->getDoctrine()
    ->getRepository('Acme:product')
    ->find($keywords);
    

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68. MAKE IT
    OPTIONAL
    

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69. A GOOD
    FRAMEWORK
    WILL HELP YOU
    

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70. $this->repository->search($keywords);
    class="Acme\ProductCatalog\ProductRepository"
    factory-service="doctrine"
    factory-method="getRepository">
    Acme:Product
    
    

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71. DON'T START
    WITH
    THE FRAMEWORK
    

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72. MAKE YOUR
    APPLICATION
    INDEPENDENT
    

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73. AND THEN
    INTEGRATE IT
    WITH
    THE FRAMEWORK
    

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74. REMEMBER!
    

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75. TDD
    IS YOUR
    FRIEND
    

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76. THANK YOU!
    

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77. Credits
    

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