I've been building a bunch of custom AS3 components for clients lately, and have run across the need to use view states within an AS3 component.

Working with states in MXML is pretty trivial, using the AddChild, RemoveChild and SetProperty tags, you can do virtually anything you need, but when working in an AS3 only environment, it becomes a bit trickier, since there are no tags. Of course, anyone who has worked with Flex for any length of time knows that MXML tags are interpreted into AS classes before the application is compiled into a SWF, so anything you can do in a tag, you can also do with pure AS.

I was looking to do the AS3 equivalent of this:

<mx:states>

    <mx:State name="minimized">

       <mx:SetProperty target="{this}" property="height" value="{this.getStyle('headerHeight')+15)}"/>

       <mx:SetProperty target="{this}" property="width" value="{this.minWidth}"/>

       <mx:SetProperty target="{this}" property="vScrollPolicy" value="off"/>

       <mx:SetProperty target="{this}" property="hScrollPolicy" value="off"/>

    </mx:State>

</mx:states>

Here is my AS3 to do the same thing:

private function buildStates():void{
    var overrides:Array = new Array();
    var newState:State = new State();
    overrides.push(makeSetProp(this,"height",this.getStyle("headerHeight")+5));
    overrides.push(makeSetProp(this,"width",this.minWidth));
    overrides.push(makeSetProp(this,"vScrollPolicy","off"));
    overrides.push(makeSetProp(this,"hScrollPolicy","off"));
    newState.name="minimized";
    newState.overrides = overrides;
    this.states = new Array(newState);
}
private function makeSetProp(target:UIComponent, property:String, value:*):SetProperty{
    var sp:SetProperty = new SetProperty();
    sp.target = target;
    sp.property = property;
    sp.value = value;
    return sp;
}

Essentially what we have is that each UIComponent has a property called states, which holds an array mx.states.State instances. Each State has an array of things to override, called "overrides." In this case, each of the overrides is a SetProperty, although, it could just as easily be AddChild or RemoveChild.