Basic question about referencing an instance.....

[bellend]

Hi all!

I came across something id just like to straighten out.


//class A is just a useful thing with public methods

var a = new A();

//class B will handle events and change a's state via mouse events, it also
should be given a reference to object a so that it can manipulate a's state.

var b = new B(a);

When i do this, i am not 100% sure what i have done.


If class Bs constuctor includes this:

private var objectToControl:A;

public function B (objectToControl:A)
{
    this.objectToControl = objectToControl;
}

Then what am i doing here? I do not seem to be able to contact 'a'. I think maybe im making a copy of 'a' into objectToControl and not actually referencing it like i want to.

I just dont know though. If i am making a copy of 'a' and assigning it to a property, then how do i achieve a reference to 'a' and not a clone of it?

[MyFriendIsATaco]

you shouldn't be making a copy of it, it should be passing along a reference, just like when you work with an array or matrix:

var a:Array = new Array(1, 2, 3, 4);
var b:Array = a;

b.push(5);

trace(a);  // 1, 2, 3, 4, 5

But I think a better way to handle this is to dispatch events from B, and have A listen for them.

[bellend]

Thanks for that matey

Can i ask you to explain further if you have the time?


Would you be able to give me an example of what you mean by dispatching events for A?

You mean inside A

this.addEventListener(event, function);

Although the way i am confused is i do not know how this works.

Does that not mean instead that 'a' instances picks up mouseOver events?.

I am not sure how to listen to events from instance a
Then dispatch those events from b

I think thats why im doing things in a messy way. No matter how much i read about events, i just cannot see the bare bones.

[5TonsOfFlax]

The event model would certainly work, but I don't think it's necessarily the best fit. I'm going to try my psychic abilities here. I'm getting a vision of code in B that looks like this:

public function doSomething(){
 a.someProperty = someValue;
}

Of course that won't work. B has no idea what "a" means. Change that to:

public function doSomething(){
 objectToControl.someProperty = someValue;
}

Now, I'm going to explain by way of example. Your real name is probably not "bellend". For this example, I'm going to pretend your real name is "Bob" (but I don't know that).

If someone told me to explain this to Bob, I'd have no idea who to talk to. But, if someone told me to explain this to bellend, well, I just did that, because I have a reference to you as "bellend".

So there you go, Bob. Make sense?

[bellend]

Thanks but now im more confused than ever!

In a new direction slightly from my thread say: A random example

A lightbulb sprite and a lightswitch sprite.

The lightbulb has a listener attached that is listening for a mouseclick to happen on lightswitch.

When the user clicks on lightswitch, this event is dispatched and the lightbulb comes on.

I dont know how to implement this if there are 2 seperate instances. This part is what i fail to understand.

[bellend]

i posted this reply twice by mistake

[5TonsOfFlax]

Sorry for confusing you Bob. In that case I would go with MyFriendIsATaco's suggestion and use event listeners.

public class LightBulb{
  ...
  private var on:Boolean = false;
  public function flipState(evt:Event = null):void{
    on = !on; //if it was on, turn off, and vice versa
  }
}

var switch:LightSwitch = new LightSwitch();
addChild(switch);
var bulb:LightBulb = new LightBulb();
addChild(bulb);

switch.addEventListener(MouseEvent.CLICK, bulb.flipState); //when switch is clicked, bulb flips.

[bellend]

!!!!!!!

Thanks!!

[MyFriendIsATaco]

Hehe, I was referring to even further by broadcasting a custom event, like: LightBulbEvent.SWITCH, and attaching a lightbulb to the listener. LightSwitch will dispatchEvent(new LightBulbEvent(LightBulbEvent.SWITCH)); or something along those lines.