Yii - 依赖注入

依赖注入 (DI) 容器是一个知道如何实例化和配置对象的容器。Yii 通过yii\di\Container 类提供 DI 容器。

它支持以下几种 DI：

• Setter 和属性注入
• PHP 可调用注入
• 构造函数注入
• 控制器动作注入

DI 容器通过类型提示支持构造函数注入：

class Object1 {
   public function __construct(Object2 $object2) {

   }
}
$object1 = $container->get('Object1');
// which is equivalent to the following:
$object2 = new Object2;
$object1 = new Object1($object2);

属性和 setter 注入通过配置支持：

<?php
   use yii\base\Object;
   class MyObject extends Object {
      public $var1;
      private $_var2;
      public function getVar2() {
         return $this->_var2;
      }
      public function setVar2(MyObject2 $var2) {
         $this->_var2 = $var2;
      }
   }
   $container->get('MyObject', [], [
      'var1' => $container->get('MyOtherObject'),
      'var2' => $container->get('MyObject2'),
   ]);
?>

对于 PHP 可调用注入，容器将使用注册的 PHP 回调来构建类的新的实例：

$container->set('Object1', function () {
   $object1 = new Object1(new Object2);
   return $object1;
});
$object1 = $container->get('Object1');

控制器动作注入是一种 DI 类型，其中依赖项使用类型提示声明。它有助于保持 MVC 控制器轻量级：

public function actionSendToAdmin(EmailValidator $validator, $email) {
   if ($validator->validate($email)) {
      // sending email
   }
}

可以使用yii\db\Container::set()方法注册依赖项：

<?php
   $container = new \yii\di\Container;
   // register a class name as is. This can be skipped.
   $container->set('yii\db\Connection');
   // register an alias name. You can use $container->get('MyObject')
   // to create an instance of Connection
   $container->set('MyObject', 'yii\db\Connection');
   // register an interface
   // When a class depends on the interface, the corresponding class
   // will be instantiated as the dependent object
   $container->set('yii\mail\MailInterface', 'yii\swiftmailer\Mailer');
   // register an alias name with class configuration
   // In this case, a "class" element is required to specify the class
   $container->set('db', [
      'class' => 'yii\db\Connection',
      'dsn' => 'mysql:host=127.0.0.1;dbname = helloworld',
      'username' => 'vladimir',
      'password' => '12345',
      'charset' => 'utf8',
   ]);
   // register a class with configuration. The configuration
   // will be applied when the class is instantiated by get()
   $container->set('yii\db\Connection', [
      'dsn' => 'mysql:host=127.0.0.1;dbname = helloworld',
      'username' => 'vladimir',
      'password' => '12345',
      'charset' => 'utf8',
   ]);
   // register a PHP callable
   // The callable will be executed each time when $container->get('db') is called
   $container->set('db', function ($container, $params, $config) {
      return new \yii\db\Connection($config);
   });
   // register a component instance
   // $container->get('pageCache') will return the same instance each time when it 
      //is called
   $container->set('pageCache', new FileCache);
?>

使用 DI

步骤 1 - 在components文件夹中创建一个名为MyInterface.php的文件，内容如下。

<?php
   namespace app\components;
   interface MyInterface {
      public function test();
   }
?>

步骤 2 - 在 components 文件夹中，创建两个文件。

First.php -

<?php
   namespace app\components;
   use app\components\MyInterface;
   class First implements MyInterface {
      public function test() {
         echo "First class <br>";
      }
   }
?>

Second.php -

<?php
   app\components;
   use app\components\MyInterface;
      class Second implements MyInterface {
      public function test() {
         echo "Second class <br>";
      }
   }
?>

步骤 3 - 现在，向 SiteController 添加一个actionTestInterface。

public function actionTestInterface() {
   $container = new \yii\di\Container();
   $container->set
      ("\app\components\MyInterface","\app\components\First");
   $obj = $container->get("\app\components\MyInterface");
   $obj->test(); // print "First class"
   $container->set
      ("\app\components\MyInterface","\app\components\Second");
   $obj = $container->get("\app\components\MyInterface");
   $obj->test(); // print "Second class"
}

步骤 4 - 访问https://127.0.0.1:8080/index.php?r=site/test-interface，您应该看到以下内容。

这种方法很方便，因为我们可以在一个地方设置类，其他代码将自动使用新的类。