Help removingChild IF child has been added!

[rogueblade]

- So I have 4 functions called by their own buttons.
Each function calls a movie clip from the library with addChild.
- When I click on one of these 4 functions I want it to remove the added children if any of the other functions had been clicked prior.
- Problem is, removeChild at the start of each function results in errors if a child had never been called yet. It's trying to remove something that isn't there.
- So I tried making a 'flag:number = 0' for each of the 4 functions. Each function begins with settings its flag to '1'
- I put a for loop at the beginning of each function saying IF any of the flags are = to 1, then remove the children.
- I don't see why that should not work, I think the error lies in my array or my for loop if statement as I still don't fully understand them.
So I will just post the code relating to the array and loop:

var flagH:Number = 0;
var flagLi:Number = 0;
var flagBe:Number = 0;
var flagBr:Number = 0;
var flagArray:Array = new Array(flagH, flagLi, flagBe, flagBr);

//hydrogenOn is the first of four each one essentially doing the same thing
function hydrogenOn(event:MouseEvent):void {
	flagH = 1;
	for (var i:int = 0; i<flagArray.length; i++) {
		if (flagArray[i].Number==1) {                     //<-- this cant be right
			table_mc.removeChild(lithium_mc);
			table_mc.removeChild(beryllium_mc);
			table_mc.removeChild(bromine_mc);
		}
	}
table_mc.addChild(hydrogen_mc);
// and the rest of the function.....

btw this is the error report:

Error #1069: Property Number not found on Number and there is no default value.
at PhoneApp_fla::MainTimeline/hydrogenOn()

[5TonsOfFlax]

As the error message says, it's actually complaining about a non-existent "Number" property. This line:

if (flagArray[i].Number==1){

is the culprit. There is no Number property of a Number.

But what you really want to solve your original problem is simply the contains function. That will let you know if it's safe to call removeChild.

[rogueblade]

yea I fixed that part forgot to update here sorry. now states:

if (flagArray[i]==1) {

problem is that the swf runs with No errors yet the for loop if statement does nothing.
What's this about a contains function?

[rogueblade]

Ok I've now worked out my flag must be called like this

flagArray[0] = 1;

and not like this

flagH = 1;

but now I am given the error

ArgumentError: Error #2025: The supplied DisplayObject must be a child of the caller.
at flash.display:: DisplayObjectContainer/removeChild()
at PhoneApp_fla::MainTimeline/hydrogenOn()

[5TonsOfFlax]

I tried to post about contains earlier, but I guess it didn't go through. contains is a method of DisplayObjectContainer which tells you if a DisplayObject is a child. You can use it to tell if you can safely call removeChild.

if (p.contains(c)){
  p.removeChild(c);
}

This will safely remove c if it is a child of p, and do nothing if it isn't.

[rogueblade]

Am I able to make c = what I have below? I want it to say:
if (p.contains(any of these children){
p.removeChild(any of the children p contains);
}

So I made an array holding my classes which are 4 movieclips

for (var i:int = 0; i<classmcArray.length; i++) {
if (table_mc.contains(classmcArray[i])){
table_mc.removeChild(classmcArray[i]);
}
}

so I made that but get the error:
Error #2007: Parameter child must be non-null.

[5TonsOfFlax]

That code looks okay, but you have null somewhere in your classmcArray.

[MyFriendIsATaco]

If I have a case where the object MIGHT not be on the stage, but I want it gone no matter what, I'll just wrap it in a try...catch block just to suppress the error:

try{ removeChild(theChild); }catch($e:Error){} 

Or if I need to use it a lot, I'll write a function that just wraps around that to keep it cleaner:

function forceRemoveChild($parent:DisplayObjectContainer, $child:DisplayObject):void
{
    try{ $parent.removeChild($child); }catch($e:Error){}
}

forceRemoveChild(this, theChild); 

[rogueblade]

I'll keep that in mind as it sounds quite useful for future work. But I actually finally figured it out with the help at another forum
got rid of all those annoying flags and arrays simply used

var currentClip:MovieClip; 

so:

function hydrogenOn(event:MouseEvent):void {
    if(currentClip != null) {
    table_mc.removeChild(currentClip);        
    }
}
    table_mc.addChild(Hydrogen_mc);
    currentClip = Hydrogen_mc;
//rest of function 

works like a charm!