Question

I have an object that is nested several levels deep which I’m referencing multiple times. Is it faster to create and set a reference to that object or does it matter?

Context
I heard that it is faster to create a local reference. This is years ago and for a Visual Basic project. But this is Flash. And the output is a SWF / bytecode. And the compiler could look at that reference and do what I’m doing so that the object does not have to be looked up each time.

For example:

public function doStuff():void {

    Model.instance.view1.button1 = button1;
    Model.instance.view1.button2 = button2;
    Model.instance.view1.button3 = button3;
    Model.instance.view1.button4 = button4;
    Model.instance.view1.button5 = button5;
    Model.instance.view1.button6 = button6;

    // more fake code referencing more something.something.something like things 

    for (var i:int;i<something.something.something.length;i++) {
        var result:Object = Controller.staticMethod(button1);
        var result2:Object = Controller.staticMethod(button1);
    }
}

Vs:

public function doStuff():void {
    var view1:View = Model.instance.view1;

    view1.button1 = button1;
    view1.button2 = button2;
    view1.button3 = button3;
    view1.button4 = button4;
    view1.button5 = button5;
    view1.button6 = button6;
}

.
Taking Baris suggestion I tested it for myself. Below are the results (though I don’t know how to interpret them into the actual difference ie ‘method 1 is .000001 faster than method 2’).

Results

Test 1

            var instance:Model = Model.instance;

            var startTime:int = getTimer();
            for(var i:int = 0; i<10000000; i++){
                instance.url = "";
            }
            trace(getTimer()-startTime); // 826, 929, 823

            var startTime:int = getTimer();
            for(var i:int = 0; i<10000000; i++){
                Model.instance.url = "";
            }
            trace(getTimer()-startTime); // 3483, 3976, 3539

Test 2

            var instance:Model = Model.instance;

            var localLogo:BitmapImage = Model.instance.logo;

            var startTime:int = getTimer();
            for(var i:int = 0; i<10000000; i++){
                localLogo = logo;
            }
            trace(getTimer()-startTime); // 2070, 2083, 2110

            var startTime:int = getTimer();
            for(var i:int = 0; i<10000000; i++){
                instance.logo = logo;
            }
            trace(getTimer()-startTime); // 2028, 2509, 2154

Answer 1

Generally, the as3 compiler is not that smart as we think. I think it does that to reduce compilation times.

This page http://upshots.org/actionscript/20-tips-to-optimize-your-actionscript gives us a rule:

5: The one-dot rule When accessing nested variables, anytime a
variable requires even one level of scope shift to discover, and is
referenced more than once, save it to local variable. In drawing
classes, you’ll often see Math.PI / 2 referenced within loops that
might iterated hundreds of times each frame – that value should be
stored in a local variable. Note that this is not true when
referencing member methods. Saving Math.PI to a variable is
appropriate; saving Math.round to a variable is not.

It does make difference, but to a software building perspective, the more readable code would be the propper way to do it, unless it’s critical code, like a physics section of your app.

Other than making time benchmarks, you can inspect the bytecode too, using this tool http://www.swfwire.com/