In ActionScript 3.0, can you use addEventListener for one class to react to the function call of another class? - actionscript-3

Question

I know how to use addEventListener for one class to react to another class's button being clicked on. What if you want to use it for a more general purpose than that? What if you want to use it to react to one of the member functions of the other class being called? Is there a syntax for that? Thanks!
Edit: Please note that I have already Googled for the answer.

Answer 1

If you want to listen for another class' member function call, you need that function call to dispatch an Event. This is as simple as...
Listener Class
addEventListener("customEvent", listenerFunc);
Dispatcher Class (extends EventDispatcher / implements IEventDispatcher)
dispatchEvent(new Event("customEvent"));
As long as the listener class is above the dispatcher class in the object hierarchy, this will work perfectly. If not, you may want to use some sort of Global EventDispatcher class and register all listeners on that.

Answer 2

You can create your own events and dispatch them from the other class and listen to them in your listening class. Here is some code
In class A (assuming it inherits EventDispatcher)
public function classAMethod():void
{
dispatchEvent(new Event("someCustomTypeForEvent"));
}
In class B (assuming it has a reference to Class A)
public function classBMethod():void
{
classA.addEventListener("someCustomTypeForEvent",customHandler);
}
public function customHandler(e:Event):void
{
trace("handle event");
}

Answer 3

It's like in JAVA for java.awt.Component instances and all Objects that extends java.awt.Component; in AS3 you may add Listeners to all Objects that extends flash.display.Sprite instances which implements methods of IEventDispatcher for you...
So, If you have a class which do not extends flash.display.Sprite, you'll have to extend EventDispatcher in order to add Listeners to your instances and handle Events...
If the class may not extend EventDispatcher, you'll have to implement the IEventDispatcher.
Here is a [class MainClass] that extends [class MovieClip]
This MainClass instance, creates :
An instance of [class ObjectA] which extends [class Object] and implements IEventDispatcher,
An instance of [class ObjectB] which extends [class EventDispatcher]
Here is the code that use the extension method and the implementation method :
I hope this quick done example will help you...
(And sorry for my English, this is not my native language.)
in MainClass.as :
package com
{
import flash.utils.getDefinitionByName;
import flash.display.MovieClip;
import flash.utils.getDefinitionByName;
import flash.utils.getQualifiedClassName;
import flash.utils.getQualifiedSuperclassName;
import com.classes.ObjectA;
import com.classes.ObjectB;
import flash.events.Event;
public class MainClass extends flash.display.MovieClip
{
private static const DEBUG:Boolean = true;
private static var instance:MainClass;
private static var instanceOfA:ObjectA;
private static var instanceOfB:ObjectB;
public function MainClass()
{
MainClass.debug("MainClass constructor called");
MainClass.debug(getClassInformations(MainClass));
MainClass.debug(getClassInformations(ObjectA));
MainClass.debug(getClassInformations(ObjectB));
instanceOfA = new ObjectA();
instanceOfB = new ObjectB();
instanceOfA.addEventListener(ObjectA.DO_SOMETHING_EVENT,onInstanceOfA_doSomething,false,0,false);
instanceOfB.addEventListener(ObjectB.DO_SOMETHING_EVENT,onInstanceOfB_doSomething,false,0,false);
instanceOfA.doSomething();
instanceOfB.doSomething();
}
public static function onInstanceOfA_doSomething(e:Event):void
{
trace("An ObjectA has Dispatched An Event of type \"" + e.type + "\"" + " on " + e.target);
}
public static function onInstanceOfB_doSomething(e:Event):void
{
trace("An ObjectB has Dispatched An Event of type \"" + e.type + "\"" + " on " + e.target);
}
public static function getDebugMode():Boolean
{
return DEBUG;
}
public static function debug(string:String)
{
if (getDebugMode())
{
trace(string);
}
}
public static function getClassInformations(someClass:Class):String
{
var clss:Object = null;
var supClss:Object = null;
clss = getDefinitionByName(getQualifiedClassName(someClass));
try
{
supClss = getDefinitionByName(getQualifiedSuperclassName(someClass));
}
catch (e:ArgumentError)
{
// Has no superClass (ex:Object)
}
if (supClss != null)
{
return ("class " + clss + " extends " + supClss);
}
else
{
return ("class " + clss);
}
}
}
}
in ObjectB.as (simplest way):
package com.classes{
import com.MainClass;
import flash.events.EventDispatcher;
import flash.events.Event;
public class ObjectB extends EventDispatcher {
public static var DO_SOMETHING_EVENT:String = "do_something_event";
private var onDoSomethingEvent:Event = new Event(DO_SOMETHING_EVENT,false,false);
public function ObjectB() {
MainClass.debug("constructor ObjectB called");
}
public function doSomething():void{
this.dispatchEvent(onDoSomethingEvent);
}
}
}
in ObjectA.as (there you must implement all the methods of the interface IEventDispatcher):
package com.classes
{
import com.MainClass;
import flash.events.IEventDispatcher;
import flash.events.EventDispatcher;
import flash.events.Event;
public class ObjectA implements IEventDispatcher
{
public static var DO_SOMETHING_EVENT:String = "do_something_event";
private var onDoSomethingEvent:Event = new Event(DO_SOMETHING_EVENT,false,false);
private var dispatcher:EventDispatcher;
public function ObjectA()
{
dispatcher = new EventDispatcher(this);
MainClass.debug("constructor ObjectA called");
}
public function doSomething():void
{
this.dispatchEvent(onDoSomethingEvent);
}
public function addEventListener(
event_type:String,
event_listener:Function,
use_capture:Boolean = false,
priority:int = 0,
weakRef:Boolean = false
):void
{
// implements addEventListener here
dispatcher.addEventListener(event_type, event_listener, use_capture, priority, weakRef);
}
public function dispatchEvent(e:Event):Boolean
{
// implements dispatchEvent here
return dispatcher.dispatchEvent(e);
}
public function removeEventListener(
event_type:String,
event_listener:Function,
use_capture:Boolean = false
):void
{
// implements removeEventListener here
dispatcher.removeEventListener(event_type, event_listener, use_capture);
}
public function hasEventListener(type:String):Boolean
{
// implements hasEventListener here
return dispatcher.hasEventListener(type);
}
public function willTrigger(type:String):Boolean
{
// implements willTrigger here
return dispatcher.willTrigger(type);
}
}
}
Note that if you extend an EventDispatcher, you may also want to override some methods.
In this case, you must use the "override keyword as :
public override function dispatchEvent (e:Event):Boolean {
// a method of EventDispatcher may be overridden if needed !
// do what you need HERE...
return dispatchEvent(e);
}
In AS3 you must specify the override keyword or you'll get an Error 1024:
"Overriding a function that is not marked for override."
When you create a new EventDispatcher through implement or extend, you may also specify additional arguments and methods to this object as:
public function ListenerObject (v:View,m:Main) {
dispatcher = new EventDispatcher(this);
view = v;
master = m;
}
public function getView ():View {
return view;
}
public function getMain ():Main {
return master;
}
then use those methods in the callback method as :
public function callback(e:Event):void{
e.target.getView ();
//...
}