Dependency Injection

A talk about dependency injection and the Symfony2 DI Container given at PHPUG Cologne / Bonn in September 2011.

Transcript

1. Dependency Injection
   

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2. Konzept
   

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3. Statt dem hier:
   

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4. public function __construct() {
   $this->dep1 = new Dependency1();
   $this->dep2 = new Dependency2();
   $this->dep3 = new Dependency3();
   }
   

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5. … nimmt man das da:
   

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6. public function __construct(
   DependencyInterface1 $dep1,
   DependencyInterface2 $dep2,
   DependencyInterface3 $dep3) {
   $this->dep1 = $dep1;
   // ...
   }
   

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7. Das ist alles.
   

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8. Warum?
   

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9. Separation of concerns
   

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10. Testbarkeit
    

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11. Übersichtlichkeit
    

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12. Praxis
    

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13. Wer braucht schon ein Framework?
    

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14. class DoctrineEntityManagerBuilder {
    public static function build() {
    $config = new Configuration();
    $config->setFoo("bar");
    $connOpts = array(
    "driver" => "pdo_sqlite",
    "path" => "database.sqlite"
    );
    return EntityManager::create(
    $connOpts, $config
    );
    }
    }
    

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15. Wildwuchs vermeiden
    

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16. class DoctrineEntityManagerBuilder {
    private static $instance;
    public function build() {
    if (empty(static::$instance)) {
    // ...
    static::$instance =
    EntityManager::create(
    $connOpts, $config
    );
    }
    return static::$instance;
    }
    }
    

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17. Symfony2 ServiceContainer
    

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18. Service?
    

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19. class DataImporter {
    private $em;
    Private $sourceUrl;
    public function __construct(
    EntityManager $em,
    $sourceUrl) {
    $this->em = $em;
    $this->sourceUrl = $sourceUrl;
    }
    public function import() {
    // ...
    }
    }
    

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20. 
    
    
    DataImporter
    
    
    
    
    
    %dataimporter.source_url%
    
    
    
    

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21. class MyExtension extends Extension {
    public function load(...) {
    $loader = new XmlFileLoader(...);
    $loader->load('services.xml');
    // Konfiguration auslesen
    // und in Container einfügen
    }
    public function getAlias() {
    return "my_extension";
    }
    }
    

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22. class MyController extends Controller {
    public function importAction() {
    $importer =
    $this->get("dataimporter");
    $importer->import();
    // ...
    }
    }
    

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23. Fragen?
    

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