Changing sprite nodes parent after TouchesEnded - ios

Question

I'm attempting to change the parent node of a sprite after it is dropped, but I'm getting a nil error.
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{
for (UITouch *touch in touches) {
CGPoint location = [touch locationInNode:self];
SKSpriteNode *gamePiece = [self pickObject];
gamePiece.position = location;
gamePiece.physicsBody.dynamic = NO;
[self addChild:gamePiece];
_currentTouch = touch;
currentGamePiece = gamePiece;
CGPoint touchLocation = [touch locationInNode:self.scene];
if(touchLocation.y > 350)
{
_bg.position = CGPointMake(_bg.position.x, _bg.position.y-2);
}
}
}
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
/* Called when a touch begins */
for (UITouch *touch in touches) {
CGPoint location = [touch locationInNode:self];
if ([touch isEqual:_currentTouch])
{
currentGamePiece.position = location;
}
CGPoint touchLocation = [touch locationInNode:self.scene];
if(touchLocation.y > 350)
{
_bg.position = CGPointMake(_bg.position.x, _bg.position.y-2);
}
}
}
-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
/* Called when a touch begins */
for (UITouch *touch in touches)
{
CGPoint location = [touch locationInNode:self];
if ([touch isEqual:_currentTouch])
{
currentGamePiece.position = location;
currentGamePiece.physicsBody.dynamic = YES;
SKAction *removeNode = [SKAction removeFromParent];
[gamePiece runAction: removeNode];
[_bg addChild:gamePiece];
}
}
}
Maybe it has something to do with the switch to "currentGamePiece", but when I try to remove "currentGamePiece" from its parent, I get an error like "attempting to add node that already has a parent". I may just not be going about it the right way. What's the problem?

Answer 1

Try replacing this code...
SKAction *removeNode = [SKAction removeFromParent];
[gamePiece runAction: removeNode];
[_bg addChild:gamePiece];
with this...
[gamePiece removeFromParent];
[_bg addChild:gamePiece];
The issue is gamePiece is added to the _gb before the SKAction has a chance to remove it from its parent. The app crashes because a node can't have two parents.