Yii 依赖注入

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

它支持以下类型的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);

通过配置支持属性注入和setter注入

<?php
   use yii\base\Object;
   class MyObject extends Object {
      public var1;
      private_var2;
      public function getVar2() {
         return this->_var2;
      }
      public function setVar2(MyObject2var2) {
         this->_var2 =var2;
      }
   }
   container->get('MyObject', [], [
      'var1' =>container->get('MyOtherObject'),
      'var2' => $container->get('MyObject2'),
   ]);
?>

在PHP可调用注入的情况下，容器将使用已注册的PHP回调函数来构建一个类的新实例−

$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依赖注入（DI）的类型，其依赖关系使用类型提示来声明。这对于使MVC控制器保持精简、轻量级和瘦身非常有用。

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

你可以使用 yii\db\Container::set() 方法注册依赖关系。

<?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 Connectioncontainer->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 classcontainer->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 whencontainer->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 - 在组件文件夹中创建一个名为 MyInterface.php 的文件，其代码如下：

<?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，将一个 actionTestInterface 添加到 SiteController 中。

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"
}