Symfony2 EventDispatcher component, eventdispatcher

In a plug-in system, plug-in A can add new methods without affecting other plug-ins, or do some preparation work before running a method, by It is not easy to implement extensions through inheritance. Due to the relationship between plug-ins, changes to plug-in A will also cause the associated plug-ins to be passively modified. Symfony2's EventDispatcher component implements the mediator mode and realizes the decoupling and association between plug-ins. For example, in the HttpKernel component, once the Response is created, it is necessary and useful to allow other modules of the system to modify it when the Response is sent to the client (for example: adding a cache field to the header). The Symfony2 kernel dispatches the kernel.response event, and the listener listening to the event can modify the Response object: a) The listener (PHP object) tells a specific dispatcher class that it wants to listen to the kernel.response event; b) At a certain moment, Symfony will tell the dispatcher to schedule the kernel.response event and pass an Event object containing the Response object into the event dispatch method EventDispatcher::dispatch() c) The dispatcher notifies all listeners listening to the kernel.response event to run, allowing these listeners to modify the Response object. How to use Events When an event is scheduled, the event will have a unique name (for example: kernel.response) and can be listened to by any number of listeners. Instantiate an Event object at the same time and pass it to all listeners. As you will see later, the Event object contains data about the scheduled event. Naming convention The event name can be any string, but it can follow the following naming conventions: * Use only lowercase characters, numbers, dots, and underscores; * Use the prefix name with a dot; * The name of the closing part uses a verb that can express the behavior of the current event; Event name and event object When the dispatcher dispatches an event to notify the listener, it will pass an Event object as a parameter to the listener. The base class Event is very simple, with only one method to stop the event from being passed to the next listener, and not much else. Usually, the data of a specific event will be saved in the Event object to facilitate passing the data to the listener. In the kernel.response event, the Event object passed to the listener is an object of the subclass FliterResponseEvent, which is a subclass of Event. FliterResponseEvent contains getReponse and setResponse methods, allowing the listener to obtain or modify the Response object. In summary: When creating a listener that listens to a specific event, a subclass of Event will be passed into the listener, and the listener can obtain and modify information through the methods of the subclass. Event dispatcher (dispatcher) Dispatcher is the core of the event scheduling system. Generally speaking, a dispatcher contains a list of listeners. When an event needs to be dispatched, the dispatcher will notify all the listeners it contains that are listening to the event.

<span>1</span> <span>use Symfony\Component\EventDispatcher\EventDispatcher;
</span><span>2</span> 
<span>3</span> $dispatcher = <span>new</span> EventDispatcher();

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Associated Listener Add a listener to the dispatcher to listen for a specific event. When the event is scheduled, the dispatcher will notify the listener to work. The dispatcher uses the addListener method to add a listener (PHP callable) to an event.

<span>1</span> $listener = <span>new</span><span> AcmeListener();
</span><span>2</span> $dispatcher->addListener(<span>'</span><span>foo.action</span><span>'</span>, array($listener, <span>'</span><span>onFooAction</span><span>'</span>));

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The addListener method has three parameters: * The name of the event that the listener needs to listen for; * Listener (a PHP callable); * An optional integer representing the priority (the higher the value, the higher the priority, the listener will be triggered earlier), the default is 0, if the priorities are the same, whoever adds it first will be triggered first;

PHP callable是指能作为参数传入call_user_func()或者传入is_callable()函数执行后返回true的PHP 变量。PHP callable可以是 \Closure实例，一个实现了__invoke方法的对象，或者是表示一个函数的字符串，或者一个表示对象方法或者类方法的数组。
 
到目前为止，我们看过把一个PHP对象作为监听器，我们也可以把Closure对象作为监听器。


<pre class="code"><span>1</span> <span>use Symfony\Component\EventDispatcher\Event;
</span><span>2</span> 
<span>3</span> $dispatcher->addListener(<span>'</span><span>foo.action</span><span>'</span>, function (Event $<span>event</span><span>) {
</span><span>4</span>     <span>//</span><span> will be executed when the foo.action event is dispatched</span>
<span>5</span> });

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In the above example, the foo.action event is dispatched, and the dispatcher calls the AcmeListener::onFooAction method and passes the Event object as the only parameter into the method.

<span> 1</span> <span>use Symfony\Component\EventDispatcher\Event;
</span><span> 2</span> 
<span> 3</span> <span>class</span><span> AcmeListener
</span><span> 4</span> <span>{
</span><span> 5</span>     <span>//</span><span> ...</span>
<span> 6</span> 
<span> 7</span>     <span>public</span> function onFooAction(Event $<span>event</span><span>)
</span><span> 8</span> <span>    {
</span><span> 9</span>         <span>//</span><span> ... do something</span>
<span>10</span> <span>    }
</span><span>11</span> }

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　In actual use, an object of a specific Event subclass is passed to the listener, such as FilterResponseEvent:

<span>1</span> <span>use Symfony\Component\HttpKernel\Event\FilterResponseEvent;
</span><span>2</span> 
<span>3</span> <span>public</span> function onKernelResponse(FilterResponseEvent $<span>event</span><span>)
</span><span>4</span> <span>{
</span><span>5</span>     $response = $<span>event</span>-><span>getResponse();
</span><span>6</span>     $request = $<span>event</span>-><span>getRequest();
</span><span>7</span> 
<span>8</span>     <span>//</span><span> ...</span>
<span>9</span> }

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创建和调度事件除了系统内置的事件，我们也可以创建和调度自定义的事件。这是很有好处的，当我们使用第三方类库的时，还有可以使不同的组件之间解耦，使系统更灵活健壮。静态的Events类假如我们要创建一个事件——store.order——当订单被创建的时候就会被触发。

<span>namespace</span><span> Acme\StoreBundle;

final </span><span>class</span><span> StoreEvents
{
    </span><span>/*</span><span>*
     * The store.order event is thrown each time an order is created
     * in the system.
     *
     * The event listener receives an
     * Acme\StoreBundle\Event\FilterOrderEvent instance.
     *
     * @var string
     </span><span>*/</span>
    <span>const</span> STORE_ORDER = <span>'</span><span>store.order</span><span>'</span><span>;
}</span>

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这个类并没有什么方法，也不做什么操作，只是定义了事件名称，方便管理和组织事件。监听这个事件的监听器都会被传入一个FilterOrderEvent对象。创建一个Event对象接着，当你调度这个新的事件的时候，会创建一个Event对象传如到dispatcher的dispatch()方法，dispatcher就把这个Event对象传给所有的监听该事件的监听器。如果我们不需要向监听器传入任何信息，那么可以使用系统默认的Symfony\Component\EventDispatcher\Event 类。然而，很多时候，我们都需要传入特定的信息到监听器，那么我们可以创建一个类继承Symfony\Component\EventDispatcher\Event。例如，我们需要在所有的监听器中传入order对象：

<span> 1</span> <span>namespace</span><span> Acme\StoreBundle\Event;
</span><span> 2</span> 
<span> 3</span> <span>use Symfony\Component\EventDispatcher\Event;
</span><span> 4</span> <span>use Acme\StoreBundle\Order;
</span><span> 5</span> 
<span> 6</span> <span>class</span><span> FilterOrderEvent extends Event
</span><span> 7</span> <span>{
</span><span> 8</span>     <span>protected</span><span> $order;
</span><span> 9</span> 
<span>10</span>     <span>public</span><span> function __construct(Order $order)
</span><span>11</span> <span>    {
</span><span>12</span>         $<span>this</span>->order =<span> $order;
</span><span>13</span> <span>    }
</span><span>14</span> 
<span>15</span>     <span>public</span><span> function getOrder()
</span><span>16</span> <span>    {
</span><span>17</span>         <span>return</span> $<span>this</span>-><span>order;
</span><span>18</span> <span>    }
</span><span>19</span> }

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所有监听器都可以通过FilterOrderEvent的getOrder方法获得order对象。调度事件 dispatcher的dispatch()方法通知监听给定的事件的所有监听器，有两个参数，一个是需要调度的事件名，另一个就是传给所有监听器的Event对象。

<span> 1</span> <span>use Acme\StoreBundle\StoreEvents;
</span><span> 2</span> <span>use Acme\StoreBundle\Order;
</span><span> 3</span> <span>use Acme\StoreBundle\Event\FilterOrderEvent;
</span><span> 4</span> 
<span> 5</span> <span>//</span><span> the order is somehow created or retrieved</span>
<span> 6</span> $order = <span>new</span><span> Order();
</span><span> 7</span> <span>//</span><span> ...
</span><span> 8</span> 
<span> 9</span> <span>//</span><span> create the FilterOrderEvent and dispatch it</span>
<span>10</span> $<span>event</span> = <span>new</span><span> FilterOrderEvent($order);
</span><span>11</span> $dispatcher->dispatch(StoreEvents::STORE_ORDER, $<span>event</span>);

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　　　　FilterOrderEvent对象作为参数传入到dispatch方法，现在，任何监听store.order事件的监听器都会接收到FilterOrderEvent对象，并通过调用getOrder方法获得order对象。

<span>1</span> <span>//</span><span> some listener class that's been registered for "store.order" event</span>
<span>2</span> <span>use Acme\StoreBundle\Event\FilterOrderEvent;
</span><span>3</span> 
<span>4</span> <span>public</span> function onStoreOrder(FilterOrderEvent $<span>event</span><span>)
</span><span>5</span> <span>{
</span><span>6</span>     $order = $<span>event</span>-><span>getOrder();
</span><span>7</span>     <span>//</span><span> do something to or with the order</span>
<span>8</span> }

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Event Subscribers 最普遍的监听事件的方法是注册一个监听器到dispatcher中，一个监听器可以监听一个或者多个事件。还有另一种监听事件的方法是使用Event SubScriber，Event SubScriber是一个PHP类，能够准确的告诉dispatcher它订阅了那些事件。实现EventSubscriberInterface接口，该接口有一个静态的方法getSubscriberdEvents。

<span>namespace</span><span> Acme\StoreBundle\Event;

use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\HttpKernel\Event\FilterResponseEvent;

</span><span>class</span><span> StoreSubscriber implements EventSubscriberInterface
{
    </span><span>public</span> <span>static</span><span> function getSubscribedEvents()
    {
        </span><span>return</span><span> array(
            </span><span>'</span><span>kernel.response</span><span>'</span> =><span> array(
                array(</span><span>'</span><span>onKernelResponsePre</span><span>'</span>, <span>10</span><span>),
                array(</span><span>'</span><span>onKernelResponseMid</span><span>'</span>, <span>5</span><span>),
                array(</span><span>'</span><span>onKernelResponsePost</span><span>'</span>, <span>0</span><span>),
            ),
            </span><span>'</span><span>store.order</span><span>'</span>     => array(<span>'</span><span>onStoreOrder</span><span>'</span>, <span>0</span><span>),
        );
    }

    </span><span>public</span> function onKernelResponsePre(FilterResponseEvent $<span>event</span><span>)
    {
        </span><span>//</span><span> ...</span>
<span>    }

    </span><span>public</span> function onKernelResponseMid(FilterResponseEvent $<span>event</span><span>)
    {
        </span><span>//</span><span> ...</span>
<span>    }

    </span><span>public</span> function onKernelResponsePost(FilterResponseEvent $<span>event</span><span>)
    {
        </span><span>//</span><span> ...</span>
<span>    }

    </span><span>public</span> function onStoreOrder(FilterOrderEvent $<span>event</span><span>)
    {
        </span><span>//</span><span> ...</span>
<span>    }
}</span>

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这个监听器类很简单，告诉了dispatcher监听了什么事件，还有监听的事件触发的方法。addSubscriber()方法把subscriber注册到dispatcher。

<span>1</span> <span>use Acme\StoreBundle\Event\StoreSubscriber;
</span><span>2</span> 
<span>3</span> $subscriber = <span>new</span><span> StoreSubscriber();
</span><span>4</span> $dispatcher->addSubscriber($subscriber);

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dispatcher准确的把Subscriber注册到EventSubscriberInterface::getSubscriberdEvents()返回的事件里，EventSubscriberInterface::getSubscriberdEvents()方法返回一个数组，数组的键对应Subscriber监听的事件，值对应这Subscriber处理该事件调用的一个方法或者一组方法。上面的例子中，一组监听器的方法对应这一个事件，同时我们也可以设置优先级来控制这组方法的执行先后顺序。当kernel.response事件被触发，<code>onKernelResponsePre, <code>onKernelResponseMid, 和 <code><span>onKernelResponsePost三个方法就会先后执行。</span> 停止事件的传递在一些情况下，监听器可以停止事件传递下去，防止后续的监听器被调用，换句话说，监听器必须通知dispatcher停止传递事件给后续的监听器。在监听器里面实现stopPropagation()方法：

<span>1</span> <span>use Acme\StoreBundle\Event\FilterOrderEvent;
</span><span>2</span> 
<span>3</span> <span>public</span> function onStoreOrder(FilterOrderEvent $<span>event</span><span>)
</span><span>4</span> <span>{
</span><span>5</span>     <span>//</span><span> ...</span>
<span>6</span> 
<span>7</span>     $<span>event</span>-><span>stopPropagation();
</span><span>8</span> }

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那么，监听了store.order事件的还没有执行的监听器就不会在被执行。通过isPropagationStopped()方法可以判断一个事件是否被停止。

<span>1</span> $dispatcher->dispatch(<span>'</span><span>foo.event</span><span>'</span>, $<span>event</span><span>);
</span><span>2</span> <span>if</span> ($<span>event</span>-><span>isPropagationStopped()) {
</span><span>3</span>     <span>//</span><span> ...</span>
<span>4</span> }

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AS3 的 EventDispatcher类

EventDispatcher is the event sender in as3. This is also a good feature compared to as2. Only objects inherited from this class can send events. dispatchEvent() is the method of sending events. For example, if you create a new object A and you want to notify other objects after certain changes have occurred in this object, you can use dispatchEvent(new Event("yourEvent")) and then you can call A in other places. Add a listener to A
A.addEventListener("yourEvent",yourfunction) This event can be customized, and the general objects are subclasses of EventDispatcher;
The following URL has official and detailed instructions. Please refer to it; help.adobe.com/...r.html

How to pass value from flex custom component to another custom component

There are two methods: 1. Directly call the object receiving the value in another component through the id and assign a value to it! ex://The value of b is Passing it to a is almost the same as the official component. If you want to pass the value to the internal object of the custom component, you can also directly call the sub-object id through the id a.text = b.text2. Through the method of custom events More flexible //Add a listening callback as a callback function where the value is to be used. When the event is fired, this method will be called. The value passed in this // can be received in LoadDataEvent.dispatcher.addEventListener("testEvent", callback );//How to write callback function callback(event:LoadDataEvent){ //event.data is the data you want. This does not necessarily depend on how your loadDataEvent is defined}//Dispatch the event where the value is transmitted, in the event can carry the value you want to pass dataLoadDataEvent.dispatcher.addEventListener(new LoadDataEvent("testEvent",data));//Definition of LoadDataEvent import flash.events.Event;
import flash.events.EventDispatcher;
/**
* Custom event class for loading data for components
* @author Yuan Jinlong
* @date 2010-07-08
*/
public class LoadDataEvent extends Event
{
public static const dispatcher:EventDispatcher=new EventDispatcher();
public var data:Object = null;
public function LoadDataEvent(type:String, data:Object=null,bubbles: Boolean=false, cancelable:Boolean=false)
{
super(type, bubbles, cancelable);
this.EVENT_NAME = type;
this.data = data;
this.typeData = typeData;
this.tempData = tempData;
}
override public function clone():Event{
return new LoadDataEvent(type, bubbles, cancelable, data);
}