Issue with removing sprites on collision

Question

I'm trying to make a very simple collision detection procedure just for test purposes.
The problem is with the send/receive information between functions

I have these lines on the update method (could be later implemented for checking what kind of subclass node is)

CCSprite *sprite = [background spriteCollisionWithRect:player.boundingBox];
if (sprite!=nil) {
    [sprite removeFromParentAndCleanup:YES];
}

and this is the spriteCollisionWithRect method

-(CCSprite*)spriteCollisionWithRect:(CGRect)bounds
{
    for (CCSprite *sprite in _spritesArray) {
        if (CGRectIntersectsRect(sprite.boundingBox, bounds)) {
            return sprite;
        }
    }
    return nil;
}

Now, this way not all the sprites are removed. It only works occasionally. But if I remove the node inside the collision method instead of returning it, it works nicely.

-(CCSprite*)spriteCollisionWithRect:(CGRect)bounds
{
    for (CCSprite *sprite in _spritesArray) {
        if (CGRectIntersectsRect(sprite.boundingBox, bounds)) {
            [sprite removeFromParentAndCleanup:YES];
        }
    }
    return nil;
}

Why is this?

Answer 1

Beyond the collection-management issue you identified, it's because your first function exits, returning a sprite, as soon as one colliding sprite is found, so no further sprites are examined on that iteration.

The version that performs the removal internally checks collision on all the sprites.

Answer 2

using an array to store the sprites to check for collision, means that if i remove some sprite, i certainly should update that array!! now i'm checking for collision always on the same sprite, even if it's removed from it's parent..

so the easiest way to fix the problem is as follows

-(CCSprite*)spriteCollisionWithRect:(CGRect)bounds
{
    for (CCSprite *sprite in _spritesArray) {
        if (CGRectIntersectsRect(sprite.boundingBox, bounds)) {
            [_spritesArray removeObject:sprite];
            return sprite;
        }
    }
    return nil;
}