Yii框架组件的事件机制原理与用法分析

public function onClicked($event)
{
  $this->raiseEvent('onClicked', $event);
}

$component->onClicked=$callback;

function methodName($event)
{
  ......
}

$component->onClicked=function($event) {
  ......
}

/**
   * Raises an event.
   * This method represents the happening of an event. It invokes
   * all attached handlers for the event.
   * @param string the event name
   * @param CEvent the event parameter
   * @throws CException if the event is undefined or an event handler is invalid.
   */
  public function raiseEvent($name,$event)
{
  //事件名称同一小写化处理
    $name=strtolower($name);
    //先查看成员变量是否有以此命名的事件
    if(isset($this->_e[$name]))
    {
      //如果有，这个成员保存的是每一个事件处理器
      //以数组的方式保存
      foreach($this->_e[$name] as $handler)
      {
        //如果事件处理器是一个字符串，那么就是一个全局函数
        if(is_string($handler))
          call_user_func($handler,$event);
        //如果不是，那么有可能是一个数组，该数组包含一个对象和方法名
        //参考http://php.net/manual/en/function.is-callable.php
        else if(is_callable($handler,true))
        {
          // an array: 0 - object, 1 - method name
          list($object,$method)=$handler;
          //如果对象是一个对象名
          if(is_string($object)) // static method call
            call_user_func($handler,$event);
          //判断对象是否有要调用的方法
          else if(method_exists($object,$method))
            $object->$method($event);
          else
            throw new CException(Yii::t('yii','Event "{class}.{event}" is attached with an invalid handler
"{handler}".',
              array('{class}'=>get_class($this), '{event}'=>$name, '{handler}'=>$handler[1])));
        }
        else
          throw new CException(Yii::t('yii','Event "{class}.{event}" is attached with an invalid handler
"{handler}".',
            array('{class}'=>get_class($this), '{event}'=>$name, '{handler}'=>gettype($handler))));
        // stop further handling if param.handled is set true
        //如果想停止继续循环获取事件的handler
//那么需要设置event的handled为true
        if(($event instanceof CEvent) && $event->handled)
          return;
      }
    }
    else if(YII_DEBUG && !$this->hasEvent($name))
      throw new CException(Yii::t('yii','Event "{class}.{event}" is not defined.',
        array('{class}'=>get_class($this), '{event}'=>$name)));
    //如果_e中没有这个成员也没关系
  }

class CEvent extends CComponent
{
  /**
   * @var object the sender of this event
   */
  public $sender;
  /**
   * @var boolean whether the event is handled. Defaults to false.
   * When a handler sets this true, the rest uninvoked handlers will not be invoked anymore.
   */
  public $handled=false;

  /**
   * Constructor.
   * @param mixed sender of the event
   */
  public function __construct($sender=null)
  {
    $this->sender=$sender;
  }
}

/**
   * Attaches an event handler to an event.
   *
   * An event handler must be a valid PHP callback, i.e., a string referring to
   * a global function name, or an array containing two elements with
   * the first element being an object and the second element a method name
   * of the object.
   *
   * An event handler must be defined with the following signature,
   * <pre>
   * function handlerName($event) {}
   * </pre>
   * where $event includes parameters associated with the event.
   *
   * This is a convenient method of attaching a handler to an event.
   * It is equivalent to the following code:
   * <pre>
   * $component->getEventHandlers($eventName)->add($eventHandler);
   * </pre>
   *
   * Using {@link getEventHandlers}, one can also specify the excution order
   * of multiple handlers attaching to the same event. For example:
   * <pre>
   * $component->getEventHandlers($eventName)->insertAt(0,$eventHandler);
   * </pre>
   * makes the handler to be invoked first.
   *
   * @param string the event name
   * @param callback the event handler
   * @throws CException if the event is not defined
   * @see detachEventHandler
   */
  public function attachEventHandler($name,$handler)
  {
    $this->getEventHandlers($name)->add($handler);
  }
  /**
   * Returns the list of attached event handlers for an event.
   * @param string the event name
   * @return CList list of attached event handlers for the event
   * @throws CException if the event is not defined
   */
  public function getEventHandlers($name)
  {
    if($this->hasEvent($name))
    {
      $name=strtolower($name);
      if(!isset($this->_e[$name]))
        //新建一个CList保存事件的处理器
        $this->_e[$name]=new CList;
      return $this->_e[$name];
    }
    else
      throw new CException(Yii::t('yii','Event "{class}.{event}" is not defined.',
        array('{class}'=>get_class($this), '{event}'=>$name)));
}