How Clone() method works and Why to Write it?

Small round up to Events basic, I think that is important 

As we know “Event” class is used as the base class for the creation of Event objects, which are passed as parameters to event listeners when an event occurs. So to make avail the Event Object and its properties we always extends Event

Basically in Event class(flash.events.Event class) there is one method called as clone()

How clone() method works?
clone() method duplicates an instance of an Event subclass. Returns a new Event object that is a copy of the original instance of the Event object.

Why To write clone() method?
When creating your own custom Event class, we must override the inherited Event.clone() method in order for it to duplicate the properties of your custom class.

What if I don’t override clone() method?
This works fine if implementation doesn’t re-dispatch the event, but as soon as we re-dispatch the event (by calling dispatchEvent(event) in a handler that is handling event), we get a TypeError: Error #1034: Type Coercion failed: cannot convert flash.events::Event@28ef5b1 to events.

Lets Produce the error

Main Application Code

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" xmlns:local="*" creationComplete="onCreationComplete()">
	<mx:Script>
		<![CDATA[
			import events.DemoCloneImportance;
			import mx.controls.Alert;
			private function onCreationComplete():void
			{
				demoCloneDispatcher.addEventListener(DemoCloneImportance.CLONE_EVENT,cloneDemoHandler);
				this.addEventListener(DemoCloneImportance.CLONE_EVENT,cloneRedispatchHandler);
			}
			
			private function cloneDemoHandler(event:DemoCloneImportance):void
			{
				Alert.show('In Dispatch Handler');
				this.dispatchEvent(event);		
			}
			
			private function cloneRedispatchHandler(event:DemoCloneImportance):void
			{
				Alert.show('In Redispatcher Handler');
			}
			
		]]>
	</mx:Script>

	<local:CloneInvokerComponent id="demoCloneDispatcher"/>
	
</mx:Application>

Component Class is as follows:

<?xml version="1.0" encoding="utf-8"?>
<!--CloneInvokerComponent.mxml-->
<mx:VBox xmlns:mx="http://www.adobe.com/2006/mxml" width="400" height="300">
	<mx:Script>
		<![CDATA[
			import events.DemoCloneImportance;
		]]>
	</mx:Script>
<mx:Metadata>
	[Event(name="CloneEventDemo", type="events.DemoCloneImportance")]
</mx:Metadata>
	<mx:Button label="Dispatch Event" id="btnDispatch" click="dispatchEvent(new DemoCloneImportance(DemoCloneImportance.CLONE_EVENT,true))"/>
</mx:VBox>

Wrong Implementation of Event Class, (Without overriding clone() method )Must avoid it

package event
{
import flash.events.Event;

public class DemoCloneImportance extends Event
{
public function DemoCloneImportance(type:String, bubbles:Boolean=false, cancelable:Boolean=false)
{
super(type, bubbles, cancelable);
}

public static const CLONE_EVENT:String = 'CloneEventDemo'		// Override the inherited clone() method.

}

}

Run the Application and we get Runtime error (Visible if Flash Debugger installed)

Now To Resolve it make Custom Event class implementation right

package event
{
import flash.events.Event;

public class DemoCloneImportance extends Event
{
public function DemoCloneImportance(type:String, bubbles:Boolean=false, cancelable:Boolean=false)
{
super(type, bubbles, cancelable);
}

public static const CLONE_EVENT:String = 'CloneEventDemo'		// Override the inherited clone() method.

override public function clone():Event {
return new DemoCloneImportance(type, true,false);
}

}

}

This is something very basic but i think most important also

Best Luck & Happy coding

Thanks and regards

Shashank Kulkarni

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