Going through each Sprite in order to update

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Going through each Sprite in order to update

(7 posts) (3 voices)

Started 2 years ago by EmmaLynn
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EmmaLynn
Member

Hello,
I am very new to Objective C and Cocos2d. I have spent most of the day trying to figure out how to do this. I tried several ways but it doesn't work. I have an Atlas Sprite Manager with lots of sprites in it. These sprites are added on a timer and will be removed when I'm done with them one at a time. The sprites are simple blocks and will be deleted when clicked. The problem is, since I don't know how many sprites there are and tagging doesn't seem to be an option because I don't know what the tags would be since they are being added and removed by the game engine. I just need to create a simple loop so I can interact with the sprites one at a time, update them and let the engine proceed to the next loop. How do I do this?

I tried the example from:
http://www.cocos2d-iphone.org/forum/topic/754#post-4442

layer *layer = [mygame node];
for(id *item in layer.children)
{
//and if I want to make sure the child is the type I want:
if([item isKindOfClass:[AtlasSprite class]]) <----- This gives me this - Warning: invalid receiver type 'id*'
{
//int x = item.position.x; <---- this errors out saying unused variable x
}
}

Then I tried to just loop through the children of the manager itself like this.

AtlasSpriteManager *mgr = (AtlasSpriteManager*) [self getChildByTag:kTagSpriteManager];
for(id *sprite in mgr.children)
{
int x = sprite.position.x; <----- Again same error
}

I think I see a problem because sprite is not really a sprite it's an id but how do I make the ID point to the sprite so I can work with it?

Posted 2 years ago #
Osiris
Member
you will probably need to track all your sprites in an NSMutableArray. That way, you will know which ones are on the board and which aren't.

When you reference a sprite in another method, you have to reference that instance somehow. The getChildByTag: seems to be the easiest way. You definitely cannot just say:

int x = sprite.position.x; unless you have defined what that sprite is first.

in my case, I created an NSMutableArray called "inPlay" so, in my collision method, I wrote:
```
- (void)collision {

	Sprite *bullet = (Sprite *)[self getChildByTag:2];

	CGRect bulletBounds = [self makeRect:bullet];
	CGRect center = CGRectMake(235, 155, 10, 10);

	// Monster Collision Detection Loop

	for(Sprite *enemy in inPlay) {

		CGRect enemyBounds = [self makeRect:enemy];

		if( !(CGRectIntersectsRect(center, enemyBounds))
		   && CGRectIntersectsRect(enemyBounds, bulletBounds) ) {

			[outPlay addObject:enemy];
....
```
That will cycle through all the enemies that are on the screen and allow you to take action on them. I can't say this is the "right" way or not, but it has worked very well for me.
Posted 2 years ago #
chrisco
Member
I haven't really looked at the code to figure out what you're doing, but "id *sprite" will definitely give you an error. Try removing the asterisk:
```
layer *layer = [mygame node];
for(id item in layer.children) {

    if([item isKindOfClass:[AtlasSprite class]]) {
        //int x = item.position.x; // You aren't doing anything with this?
    }

}
```
Again, your code still might not do what you want, but you won't receive the error you're getting now...
Posted 2 years ago #
EmmaLynn
Member

Thank you all for the quick replies! I'm going to try these suggestions out. I'm translating this code from a non object oriented programming language and this is a bit tricky! :o)

Posted 2 years ago #
EmmaLynn
Member

Osiris - Thanks for the tip. I really like this idea, I think this will work. So you don't actually delete the enemy sprites you just take them out of play and recycle them. Thats interesting. It looks as though you make 2 NSMutableArrays. I see in your code you added the hit enemy to the outplay array do you also remove the enemy from the inplay array in that method? I would assume you do.

chrisco - thanks for the tip it did fix my warning. I'll have to remember that, I thought I needed the * because I was declaring a new variable. I'm still getting used to objective c. I'm not sure when to use the asterisk and when not to. Of course it doesn't do what I want the code to do I think Osiris' suggestion is the way to go as far as achieving my objective.

Posted 2 years ago #
Osiris
Member
@EmmaLynn I accumulate the hit enemy in the outPlay array and then do the following outside the loop:
```
if ([outPlay count] > 0) {

		[inPlay removeObjectsInArray:outPlay];
		[outPlay removeAllObjects];
	}
```
you get all sorts of nasty errors if you try to remove an element of an NSMutable array that is being traversed. I learned the hard way!
Posted 2 years ago #
EmmaLynn
Member

Thanks allot!! That just saved me a ton of time!!

Posted 2 years ago #

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