Question

How can I access instance variables in closure（inner function） for this style: this['varName']?

public class Test extends Sprite
{
    private var a0:String = 'a0';
    private var a1:String = 'a1';
    private var a2:String = 'a2';

    public function Test()
    {
        var testFun:Function = function(evt:Event):void
        {
            for(var i:uint = 0; i < 3; i += 1)
            {
                trace(this['a'+i]);//how to access instance variables?
            }
        };
        this.addEventListener(Event.ENTER_FRAME, testFun);
    }
}

Answer 1

Square brackets can be used to access properties of an Object (everything) exactly as you’ve done above:

object[propertyName]

Or set properties, assuming that your class is either dynamic or already has the property you’re trying to set:

object[propertyName] = 10;

With an Object, you’re actually able to use a for(String in Object) loop to output all of the properties you want:

var object:Object = {
    test: "string",
    another: 5
};

for(var i:String in object)
{
    trace(i + ": " + object[i]);
}

As for your current code, restructure it:

public class Test extends Sprite
{
    private var a0:String = 'a0';
    private var a1:String = 'a1';
    private var a2:String = 'a2';

    public function Test()
    {
        testFun();
    }

    public function testFun():void
    {
        for(var i:uint = 0; i < 3; i += 1)
        {
            trace(this['a'+i]);
        }
    }
}

---

If you must retain your inner function, parse a reference to your current instance of Test into it:

var testFun:Function = function(subject:Test):void
{
    for(var i:uint = 0; i < 3; i += 1)
    {
        trace(subject['a'+i]);//how to access instance variables?
    }
};

And then:

testFun(this);