Create an endless animation with pop? - ios

Question

When using the Coreanimation framework I can set an animation to repeat. I want to set a button to an "attract attention" mode which should make him grow and shrink by a small amount to get the users attention.
I already chained the grow and shrink animations via completion blocks. The question is if and how I can start the first animation from the second animation's completion block.
I do get the following warning which does make sense. What is an elegant solution to this problem? I'm not a fan of creating timers for stuff like this.
Capturing 'scaleAnimation' strongly in this block is likely to lead to
a retain cycle
- (void)attractAttention:(BOOL)flag{
_attractAttention = flag;
float resizeValue = 1.2f;
// Grow animation
POPSpringAnimation *scaleAnimation = [POPSpringAnimation animationWithPropertyNamed:kPOPLayerScaleXY];
scaleAnimation.fromValue = [NSValue valueWithCGSize:CGSizeMake(1.0f, 1.0f)];
scaleAnimation.toValue = [NSValue valueWithCGSize:CGSizeMake(resizeValue, resizeValue)];
scaleAnimation.completionBlock = ^(POPAnimation *anim, BOOL finished) {
// Grow animation done
POPSpringAnimation *scaleAnimationDown = [POPSpringAnimation animationWithPropertyNamed:kPOPLayerScaleXY];
scaleAnimationDown.fromValue = [NSValue valueWithCGSize:CGSizeMake(resizeValue, resizeValue)];
scaleAnimationDown.toValue = [NSValue valueWithCGSize:CGSizeMake(1.0f, 1.0f)];
scaleAnimationDown.completionBlock = ^(POPAnimation *anim, BOOL finished) {
// Shrink animation done
if (_attractAttention) {
[self.layer pop_addAnimation:scaleAnimation forKey:#"scaleUpAnimation"];
}
};
[self.layer pop_addAnimation:scaleAnimationDown forKey:#"scaleDownAnimation"];
};
[self.layer pop_addAnimation:scaleAnimation forKey:#"scaleUpAnimation"];
}
Edit:
I also tried to create a weak reference of the animation. This removes the error, but the animations do not work anymore:
__weak typeof(scaleAnimation) weakAnimation = scaleAnimation;

Answer 1

You can also use the properties autoreveres and repeatCount to achieve the same result without use blocks. It reduces the complexity:
POPSpringAnimation *scaleAnimation = [POPSpringAnimation animationWithPropertyNamed:kPOPLayerScaleXY];
scaleAnimation.toValue = [NSValue valueWithCGSize:CGSizeMake(0.5, 0.5)];
scaleAnimation.springBounciness = 0.f;
scaleAnimation.autoreverses = YES;
scaleAnimation.repeatCount=HUGE_VALF;
[layer pop_addAnimation:scaleAnimation forKey:#"scale"];
Even better, if you check this class https://github.com/facebook/pop/blob/master/pop/POPAnimation.h you will see there is a repeatForever property, so you could replace repeatCount by it:
scaleAnimation.repeatForever=YES;

Answer 2

Edited:
Do not use this solution. The POP framework has been updated with a “repeat” flag. It was not available when I first encountered this problem.
I solved it by a very easy work around:
- (void)attractAttention:(BOOL)flag{
_attractAttention = flag;
if (_attractAttention){
[self animatePop];
}
}
- (void)animatePop{
float resizeValue = 1.2f;
// Grow animation
POPSpringAnimation *scaleAnimation = [POPSpringAnimation animationWithPropertyNamed:kPOPLayerScaleXY];
scaleAnimation.fromValue = [NSValue valueWithCGSize:CGSizeMake(1.0f, 1.0f)];
scaleAnimation.toValue = [NSValue valueWithCGSize:CGSizeMake(resizeValue, resizeValue)];
scaleAnimation.completionBlock = ^(POPAnimation *anim, BOOL finished) {
// Grow animation done
POPSpringAnimation *scaleAnimationDown = [POPSpringAnimation animationWithPropertyNamed:kPOPLayerScaleXY];
scaleAnimationDown.fromValue = [NSValue valueWithCGSize:CGSizeMake(resizeValue, resizeValue)];
scaleAnimationDown.toValue = [NSValue valueWithCGSize:CGSizeMake(1.0f, 1.0f)];
scaleAnimationDown.completionBlock = ^(POPAnimation *anim, BOOL finished) {
// Shrink animation done
if (_attractAttention) {
[self animatePop];
}
};
[self.layer pop_addAnimation:scaleAnimationDown forKey:#"scaleDownAnimation"];
};
[self.layer pop_addAnimation:scaleAnimation forKey:#"scaleUpAnimation"];
}