Setting masks with AS

Question

What am I doing wrong?
I have a MC in my library with a linkage identifier of
"mask". And I have a bunch of MCs on my stage with a instance names
of line_0, line_1, line_2.... etc.
Somehow the mask it not getting set. What am I doing wrong?
for (var i:Number = 0; i < numOfLines; i++){
this.attachMovie("mask", ["mask_" + i],
this.getNextHighestDepth(), {_x:647, _y:1165});
this["line_" + i].setMask("mask_" + i);
Thanks a lot for any help!

Answer 1

I think the problem is with your attachMovie line,
specifically the second argument. That is where you pass in the
name of the newly attached clip. It doesn't need the array brackets
around it.
However your setMask line where you are passing in the name
of the recently attached mask clip will need them!
this["line_"+i].setMask(this["mask_"+i]);
That is because in that case you need to tell flash to look
inside the current timeline (this) and look for the item named
"mask_"+i. Get it? When you give the name, it only needs a string
for the name, because you are telling it where to attach with the
this before the attachMovie. But afterwords you have to tell flash
where to look so then you do need the array notation.
BUT, there is a shortcut that is very useful.
var curLine:MovieClip=this["line_"+i];
var
curMask:MovieClip=this.attachMovie("mask","mask"+i,100+i,{yourobject});
curLine.setMask(curMask);
By defining temporary variables to be your line and your
mask, you can make the code easier to read and manage. Notice the
first one I just use the same code you've got, but assign it to a
variable. This is escpecially good if you are going to use that
several times. I don't know about you, but I have trouble always
typing the square brakets, the quotes, the plus and the variable in
the right order without a type. In this case you type it once and
then use the much easier to read and type curLine over and over.
In the second line, I rely on a how attachMovie works. If you
look it up in the help files, there is a line where it will tell
you that attachMovie returns a reference to the movie it just
attached. In fact many methods return things and you can either
ignore them or use them if you need them. In this case I capture
that return and assign it to curMask. Then again, I can always be
sure that I've got the correct mask by using the simple curMask.
Tricky, huh?