UIView animation - Objective-C. Will this animation cause a stack overflow exception? - ios

Question

I have a method with three animation blocks, which animates two UIImageViews. Will this code cause a stack overflow exception in the future?
I mean recursive blocks. I need to animate them by order. The first big image should fade in, then a smaller image should fade in, and then both images should fade out, and animation should start again.
- (void)startAnimation {
[UIView animateWithDuration:0.3 animations:^{
[_bigImage setAlpha:1];
}
completion:^(BOOL finished) {
[UIView animateWithDuration:0.3 animations:^{
[_mediumImage setAlpha:1];
}
completion:^(BOOL finished1) {
[UIView animateWithDuration:0.2 animations:^{
[_mediumImage setAlpha:0];
[_bigImage setAlpha:0];
}
completion:^(BOOL finished3) {
[self startAnimation];
}];
}];
}];
}

Answer 1

What you posted should work fine. Yes, you could also do it using CAAnimations, but those are harder to figure out.
I disagree with dasdom. I think your current approach is reasonable.
I do find nested animateWithDuration: methods to be hard to figure out. It's easy to get lost in the nested block syntax.
Instead, you could add an integer or enum instance variable that keeps track of the animation step, and have your method invoke different animation code for each step, then call itself again in each animation block:
In your header:
typedef enum
{
first,
second,
third,
done
} animationSteps
#interface MyClass
{
animationSteps currentStep
}
The .m file:
- (void)doAnimation
{
[UIView animateWithDuration:0.3 animations:^
{
switch (currentStep)
{
case first:
[_bigImage setAlpha:1];
break;
case second:
[_mediumImage setAlpha:1];
break;
case third:
[_mediumImage setAlpha:0];
[_bigImage setAlpha:0];
break;
}
}
completion:^(BOOL finished)
{
currentStep++;
if (currentStep == done)
currentStep = first;
[self doAnimation];
}
];
}