一项功能与多项功能的性能

Question

I have many drag and drop objects on the stage, and the default code snippet adds a new event listener and function to the stage for each object:

stage.addEventListener(MouseEvent.MOUSE_UP, fl_ReleaseToDrop);
function fl_ReleaseToDrop(event:MouseEvent):void { instance_1.stopDrag(); }
stage.addEventListener(MouseEvent.MOUSE_UP, fl_ReleaseToDrop_1);
function fl_ReleaseToDrop_1(event:MouseEvent):void { instance_2.stopDrag(); }
....

Would it be better or worse to put them all into one listener?

stage.addEventListener(MouseEvent.MOUSE_UP, fl_ReleaseToDrop);
function fl_ReleaseToDrop(event:MouseEvent):void {
  instance_1.stopDrag();
  instance_2.stopDrag();
  ....
}

Answer 1

One function call is surely faster than multiple function calls. However, the difference here is going to be negligible.

From a code readability stand-point, I would say the single function call you've shown is better.

---

Generally, the way I like to do drag-and-drop is to add the mouseUp handler when I start the drag, and remove it immediately when dragging is completed. For example:

instance1.addEventListener(MouseEvent.MOUSE_DOWN, mouseDown);
instance2.addEventListener(MouseEvent.MOUSE_DOWN, mouseDown);
instance3.addEventListener(MouseEvent.MOUSE_DOWN, mouseDown);

function mouseDown(e:MouseEvent):void {
    Sprite(e.currentTarget).startDrag();
    stage.addEventListener(MouseEvent.MOUSE_UP, mouseUp);
}

function mouseUp(e:MouseEvent):void {
    stopDrag();
    stage.removeEventListener(MouseEvent.MOUSE_UP, mouseUp);
}

Answer 2

For a Flash timeline easy and efficient solution you simply keep reference to your object and that's about it:

stage.addEventListener(MouseEvent.MOUSE_UP, mouseUp);
instance1.addEventListener(MouseEvent.MOUSE_DOWN, mouseDown);
instance2.addEventListener(MouseEvent.MOUSE_DOWN, mouseDown);
instance3.addEventListener(MouseEvent.MOUSE_DOWN, mouseDown);
var draggedObject:Sprite;

function mouseDown(e:MouseEvent):void 
{
    draggedObject = e.currentTarget as Sprite;
    if(draggedObject)
    {
        draggedObject.startDrag();
    }        
}

function mouseUp(e:MouseEvent):void 
{
    if(draggedObject)
    {
        draggedObject.stopDrag();
        draggedObject = null;
    } 
}