Question

im new to programming, i have been experimenting with cocos2d, heres the problem, i have made a simple game, device in portrait, it has falling sprites, and i want the sprite to disappear when the position of the top of the sprite < screen.height/2 how can this be done?

heres some code you may be interested in:

this is the falling sprite, it falls from the top of the screen to the bottom

-(void)addRock {

CCSprite *rock = [CCSprite spriteWithFile:@"rock.png" 
                                     rect:CGRectMake(0, 0, 27, 40)]; 

// Determine where to spawn the target along the X axis
CGSize winSize = [[CCDirector sharedDirector] winSize];
int minX = rock.contentSize.width/2;
int maxX = winSize.width - rock.contentSize.width/2;
int rangeX = maxX - minX;
int actualX = (arc4random() % rangeX) + minX;

// Create the target slightly off-screen along the right edge,
// and along a random position along the X axis as calculated above
rock.position = ccp(actualX, 500);
[self addChild:rock];

// Determine speed of the target
int actualDuration = spriteDuration;//speed of sprite

// Create the actions
id actionMove = [CCMoveTo actionWithDuration:actualDuration position:ccp(actualX,-winSize.height+ rock.contentSize.height)];
id actionMoveDone = [CCCallFuncN actionWithTarget:self selector:@selector(spriteMoveFinished:)];
[rock runAction:[CCSequence actions:actionMove, nil]];

}

when the sprite move has finished

-(void)spriteMoveFinished:(id)sender {
CCSprite *sprite = (CCSprite *)sender;
[self removeChild:sprite cleanup:YES];

}

Answer 1

To fade your sprite out halfway of the Animation you can use CCSpawn to combine the falling animation with the fadeOut. But as you want it to fade out after a given time, you need to create a Sequence of CCDelayTime and CCFadeOut.

double fadeStart = 0.5;
id wait    = [CCDelayTime actionWithDuration: actualDuration * fadeStart];
id fadeOut = [CCFadeOut actionWithDuration: actualDuration * (1.0 - fadeStart)];
id waitThenFade = [CCSequence actions: wait, fadeOut, nil];

id actionMove = ...;
id fullAnimation = [CCSpawn actions:actionMove, waitThenFade, nil];

[rock runAction:[CCSequence actions:fullAnimation, actionMoveDone, nil]];

In case you want the fading to start earlier or later you simply have to move the fadeStart value. 0 will start immediately, 1 will actually not fade, so better pick a value in between.