Making this AS2 code work in AS3 - please help!

[llamarama]

Hi everyone,

I found this code on a forum which allows for an undo and erase button for a drawing application (and is perfect for what I need) but it's in AS2 and I can barely make sense of it:

_root.attachMovie("canvas", "canvas", 0);
d = 0;
_root.strokes = new Array();
_root.canvas.onPress = function() {
	if (deleted) {
		_root.attachMovie("canvas", "canvas", 0);
	}
	d++;
	_root.strokes.push("stroke"+d);
	_root.canvas.createEmptyMovieClip("stroke"+d, d);
	_root.canvas["stroke"+d].moveTo(_xmouse, _ymouse);
	_root.canvas["stroke"+d].lineStyle(0, 0x000000, 100);
	this.onEnterFrame = function() {
		_root.canvas["stroke"+d].lineTo(_xmouse, _ymouse);
	};
};
_root.canvas.onRelease = function() {
	this.onEnterFrame = null;
};
_root.canvas.onReleaseOutside = function() {
	this.onEnterFrame = null;
};
buttonUndo.onPress = function() {
	if (d != 0) {
		_root.canvas["stroke"+d].removeMovieClip();
		d--;
		_root.strokes.pop();
	}
};
buttonErase.onPress = function() {
	for (i=1; i<=_root.strokes.length; i++) {
		_root.canvas["stroke"+i].removeMovieClip();
	}
};

This bit in particular confuses me and I have no idea how to turn it into working AS3 code:

 	_root.strokes.push("stroke"+d);
	_root.canvas.createEmptyMovieClip("stroke"+d, d);
	_root.canvas["stroke"+d].moveTo(_xmouse, _ymouse);
	_root.canvas["stroke"+d].lineStyle(0, 0x000000, 100);

I just don't understand how it's adding the lines being drawn to the strokes array. If anyone could help me get it working, I would really appreciate it, as I'll fail the university module if I can't get the array working

[llamarama]

Ok, kinda worked it out, now new problem...

   function startDraw(event:MouseEvent):void {
    if (inDrawingArea == true) { 
     noOfLines++; 
     var newLine_mc = new MovieClip();
     newLine_mc.name = "newLine_mc"+noOfLines;
     line.graphics.moveTo(mouseX, mouseY);   
     lines.push(newLine_mc);
     areDrawing = true;  
    }
   }   
   function doDraw(event:MouseEvent):void {
    // Only draw if mouse is down
    if(areDrawing == true) {
     newLine_mc.graphics.lineTo(mouseX, mouseY);
     addChild(newLine_mc);   
     setChildIndex(newLine_mc, 0);
    }
   }  
   function stopDraw(event:MouseEvent):void {
    areDrawing = false;   
   }   

   function undoAction(event:MouseEvent):void { 
    if (lines.length != 0) {   
     i = lines.length;  
     lines.pop();
     removeChild(lines[i]);  
    }
   }

With this approach when I hit undo it seems like it can't find the movieclips that have been created because I get the error...

TypeError: Error #2007: Parameter child must be non-null.
 at flash.display::DisplayObjectContainer/removeChild()

I put a load of traces in and I know it's adding them to the array where it's meant to, and the pop method is successfully removing them from the array but it's just not removing them from the stage. I can't work it out.

[5TonsOfFlax]

You need to call removeChild before pop, or else save the result of pop to pass to removeChild. Once you pop the last item from lines, lines[i] is undefined.

[llamarama]

Sadly, I noticed that one myself and tried it and still the same error exists.

[5TonsOfFlax]

What exactly did you try?
You know that lines[lines.length] is always undefined, right? Array indices start at 0, so if it has 5 elements in it the length is 5, but the last element is at 4.

try this:

   function undoAction(event:MouseEvent):void { 
    if (lines.length != 0) {   
     removeChild(lines.pop());  
    }
   }

[llamarama]

I meant moving removeChild to before pop. That code works perfectly though, thank you very much! I'm not a coder really so I struggle with this kind of thing.