Passing Additional Parameters with Events

What's the best way to pass additional parameters with.. let's say.. a mouseclick?

So, for example... the user clicks on a button and I want to pass the value 10 along with it.. so, whenever the buttonClicked function is called it has that value to use.

I know that you can create custom events by making a subclass of the Event class. And I know that you can dispatch the custom events to where you can access additional parameters by doing something like:

PHP Code:

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dispatchEvent(new CustomEvent("action", 10)); 


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CustomEvent's constructor would look something like:

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public function CustomEvent(_type:String, _val:Number);
   super(type);
   val = _val;
} 


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And later on you can access the val by doing something like:

PHP Code:

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function buttonClicked(evt:CustomEvent) {
   trace(evt.val);
} 


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But in order to do that, you'd have to do something like:

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button.addEventListener("buttonClick", buttonClicked);
dipatchEvent(new CustomEvent("buttonClick", 10)); 


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You have to dispatch the event yourself in order to pass that extra parameter.

So, how could I pass parameters when the user actually does click on the button?

I've thought about just adding a regular MouseEvent.MOUSE_DOWN and dispatching the event from that function... but I lose the values that I need to pass through.

I've also thought about creating a local listener function.. something like

PHP Code:

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var val:uint = 10;
button.addEventListener(MouseEvent.MOUSE_DOWN, function buttonClicked(e:Event):void { dispatchEvent("buttonClick", val); }); 


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Would that work, though? I can't test it out right now. Only brainstorming.

Any help is appreciated.

Dispatching from the button is probably your best bet. You could have one of the args for your CustomEvent be the MouseEvent passed through. That is:

Code:

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function CustomEvent(type:String, val:Number, OrigEvent:MouseEvent){

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Then, you would dispatch the event in your handler:

Code:

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function buttonClicked(e:MouseEvent){
    dispatchEvent(new CustomEvent("buttonClicked", 10, e));
}

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You could also pass the properties you need into your CustomEvent

Code:

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function buttonClicked(e:MouseEvent){
    var customEvent = new CustomEvent(buttonClicked, e.localX, val);
    dispatchEvent(customEvent);
}

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Of course, you'd have to add the corresponding args for the values you're passing through to your CustomEvent class.

That's a good idea with passing the MouseEvent into the CustomEvent as well. I didn't think of that.

My main problem now seems to be scope.. accessing the variables I want to pass through to the custom event.

I suppose I could try doing the local function used just to dispatch the custom event.

At the top of your class, declare

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private var _val:Number;

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Then you'll have access to it in all Class functions (including buttonClicked).


I'd need to see more of your code to understand better how to help. =)

Oh, I know.. I could do that.. It would just be kind of unnecessary.

As an example:

Say you have 10 buttons all stored in an array.

You want to loop through each button and assign a MouseEvent for the MouseEvent.MOUSE_DOWN

PHP Code:

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for(var i = 0; i < buttons.length; i++) {
   var button:Button = buttons[i];
   button.addEventListener(MouseEvent.MOUSE_DOWN, buttonClicked);
} 


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I mean.. that would work all fine and dandy.

But, what if the button was just a property of an object and there was an array of objects. Let's just call them TestObjects for this example.

so:

PHP Code:

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for(var i = 0; i < testObjects.length; i++) {
   var button:Button = testObjects[i].button;
   button.addEventListener(MouseEvent.MOUSE_DOWN, buttonClicked);
} 


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How would I know which button was clicked out of the array? I'm thinking I have to pass an index to the array. That way.. when the button is clicked.. the correct testObject can do whatever it needs to do.

Another example:

Say I have an array of Image objects who have filename, xpos, and ypos properties.

I'm looping through the array of Image objects and create a Loader and URLRequest to load the image from the filename. Once it's done loading, I want to move it's xpos and ypos. I'd have to pass the xpos and ypos along with the function.. but how would I do that? Again, I think I'd need a local function.

PHP Code:

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loader.contentLoaderInfo.addEventListener("imageLoaded");
loader.contentLoaderInfo.addEventListener(Event.COMPLETE, function eventComplete(e:Event):void { dispatchEvent(new CustomEvent("imageLoaded", xpos, ypos); }); 


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i was unaware you would write a function inline with addEventListener like that. i thought you'd need to call an external function.

anyway, there is a MouseEvent.target property that will tell you which object was clicked on. so if you store your variables in the button (buttons[i].ypos), you can use event.target.ypos to access them.


also, use bubbling. rather than adding an event listener for each, store the buttons in a parent display object and add your event handling to the parent.

MainTimeline
-buttonHolder
--button1
--button2
--. . .
--buttonN

buttonHolder will receive events from its children. so buttonHolder.addEventListener is the same as button1.addEventListener . . . buttonN.addEventListener

I was just trying to avoid having to create a new class and, instead, pass parameters accordingly. Because if I'm going to add properties, I'd rather create a strict class for the object.

Hm. I didn't know that. I'll give it a shot, thanks.

i dont see a disadvantage to writing a button class. add the properties you need and nobody gets hurt =)

better than stressing about it. (i get in the same -how can i do this cleanly- thought process too, but it usually turns out if i followed my intuition i'd be in good shape)