Syncing sprite animations in cocos2d - cocos2d-iphone

Question

Every now and then I add some pulsating sprites to my scene like so:
CCSpriteBatchNode *batch = (CCSpriteBatchNode*) [scene getChildByTag: foo1];
sprite = [CCSprite spriteWithBatchNode:batch rect:CGRectMake(0, 0, 128, 128)];
sprite.position = foo2
CCTintTo *a = [CCTintTo actionWithDuration: .5 red:128 green: 128 blue: 128];
CCTintTo *b = [CCTintTo actionWithDuration: .5 red:255 green: 255 blue: 255];
[sprite runAction:[CCRepeatForever actionWithAction:
[CCSequence actionOne: a two: b]]];
[batch addChild: sprite];
I would like to have all my sprites pulsating in sync, how do I go about this?

Answer 1

hmmm ... not easy. The only way i'd see of doing that is to schedule a 'flasherRamp' like so:
in .h
NSMutableArray *flashers;
in .m, init method
flashers = [[NSMutableArray array] retain]; // choose your own ARC flavor, if you retain
// dont forget to release in dealloc
[self schedule:#selector(flasherRamp) interval:1.0f];
in .m, where you create the sprite
foo2.visible=NO;
[flashers addObject foo2];
finally
-(void) flasherRamp {
for (CCSprite *flasher in flashers) {
CCTintTo *a = [CCTintTo actionWithDuration: .5 red:128 green: 128 blue: 128];
CCTintTo *b = [CCTintTo actionWithDuration: .5 red:255 green: 255 blue: 255];
[flasher runAction:[CCRepeatForever actionWithAction:
[CCSequence actionOne: a two: b]]];
flasher.visible=YES;
}
[flashers removeAllObjects];
}
ps. there could be some drift eventually, depending on how long this goes on for.
pps. from a usability perspective, this may not be a good idea if there is some causality between the appearance of the flashing sprites and some 'asynchronous' gaming event that may induce a delay of up to 1 second between the triggering event and the actual appearance of the flasher.
ob cit. : coded from memory, not tested, but should be close.

Answer 2

I would avoid using CCRepeatForever in this case.
Create an enum defining the current tint state (tintGray, tintWhite, tintDone), then create a scheduled selector that checks the state.
Once the state is complete, repeat the actions, but for every child of the batchnode (assuming those are the only children).
To schedule the selector, place the following in your init or other loading method:
// be sure to schedule the interval at a fast enough rate
[self schedule:#selector(tick:) interval:0.1f];
Then define the method as follows:
-(void)tick:(ccTime)dt
{
if(tintState == tintDone)
{
[self unschedule:#selector(tick:)];
[self tinter];
}
}
Then to schedule the tint actions for all sprites:
-(void)tinter
{
// could init and reuse this somewhere else to save on allocs
CCSequence *actions = [CCSequence actions:
[CCCallBlockN actionWithBlock:^(CCNode* node)
{
tintState = tintGray;
}],
[CCTintTo actionWithDuration: .5 red:128 green: 128 blue: 128],
[CCCallBlockN actionWithBlock:^(CCNode* node)
{
tintState = tintWhite;
}],
[CCTintTo actionWithDuration: .5 red:255 green: 255 blue: 255],
[CCCallBlockN actionWithBlock:^(CCNode* node)
{
tintState = tintDone;
}],
nil];
CCSpriteBatchNode *batch = (CCSpriteBatchNode*) [scene getChildByTag: foo1];
for (CCSprite *flasher in batch.children)
{
[flasher stopAllActions];
[flasher runAction:actions];
}
// reschedule tick checking
[self schedule:#selector(tick:) interval:0.1f];
}
Obviously this isn't perfect, as the flag will be driven by the first sprite to complete the tinting, but the delay should be negligible. If you want to make sure they all finish, just change the flag to a running count of the number of sprites, so "tinter" only gets called once tintState is equal to the number of sprites in the batchnode.