Action类，控制器中方法的基类：
namespace yii\base;
use Yii;
/**
* Action is the base class for all controller action classes.
* Action是所有控制器方法的基类
* Action provides a way to reuse action method code. An action method in an Action
* class can be used in multiple controllers or in different projects.
* Action提供了一种重用代码的方法，一个Action类中的方法可以被多个控制器或不同的项目调用
* Derived classes must implement a method named `run()`. This method
* will be invoked by the controller when the action is requested.
* 驱动类必须实现run（）方法，该方法在action被请求的时候被控制器调用
* The `run()` method can have parameters which will be filled up
* with user input values automatically according to their names.
* 如果请求带有参数，run方法会自动带参数运行，例如：
* For example, if the `run()` method is declared as follows:
*
* ```php
* public function run($id, $type = 'book') { ... }
* ```
*
* And the parameters provided for the action are: `['id' => 1]`.
* Then the `run()` method will be invoked as `run(1)` automatically.
*
* @property string $uniqueId The unique ID of this action among the whole application. This property is
* read-only.
*
* @author Qiang Xue <qiang.xue@gmail.com>
* @since 2.0
*/
class Action extends Component
{
/**
* @var action的ID
*/
public $id;
/**
* @var Controller|\yii\web\Controller 当前action的控制器
*/
public $controller;
/**
* Constructor.
* 构造函数，用于初始化action 的ID和控制器，并且调用component的构造方法初始化对象
*
* @param string $id the ID of this action
* @param Controller $controller the controller that owns this action
* @param array $config name-value pairs that will be used to initialize the object properties
*/
public function __construct($id, $controller, $config = [])
{
$this->id = $id;
$this->controller = $controller;
parent::__construct($config);
}
/**
* Returns the unique ID of this action among the whole application.
* 用于取得当前action的唯一ID 形式为controller ID/action ID
* @return string the unique ID of this action among the whole application.
*/
public function getUniqueId()
{
return $this->controller->getUniqueId() . '/' . $this->id;
}
/**
* Runs this action with the specified parameters.
* This method is mainly invoked by the controller.
* 用指定的参数运行，该方法主要被控制器调用
*
* @param array $params the parameters to be bound to the action's run() method.
* @return mixed the result of the action
* @throws InvalidConfigException if the action class does not have a run() method
*/
public function runWithParams($params)
{
if (!method_exists($this, 'run')) {//如果run方法不存在，抛出异常
throw new InvalidConfigException(get_class($this) . ' must define a "run()" method.');
}
$args = $this->controller->bindActionParams($this, $params);//绑定参数
Yii::trace('Running action: ' . get_class($this) . '::run()', __METHOD__);//记录trace信息
if (Yii::$app->requestedParams === null) {
Yii::$app->requestedParams = $args;//如果是命令行运行，按命令行方式获取参数
}
if ($this->beforeRun()) {//调用run的前置操作
$result = call_user_func_array([$this, 'run'], $args);//用php内置函数带参数执行run方法
$this->afterRun();//调用后置操作
return $result;//返回结果
} else {
return null;
}
}
/**
* This method is called right before `run()` is executed.
* You may override this method to do preparation work for the action run.
* If the method returns false, it will cancel the action.
* run方法的前置方法，通常在子类中重写来实现某些前置功能
*
* @return boolean whether to run the action.
*/
protected function beforeRun()
{
return true;
}
/**
* This method is called right after `run()` is executed.
* You may override this method to do post-processing work for the action run.
* run方法的后置方法，通常在子类中重写来实现某些后置功能
*
*/
protected function afterRun()
{
}
}