Correct way to stack UIView animations and blocks? - ios

Question

I've only worked a bit with UIView animations and blocks, basically one step animations. I'd like to stack a few steps into a sequence. The code below seems to be working but I'm wondering if this is the right approach and/or if there are any issues/limitations with placing blocks within blocks.
Blocks seem great though the code formatting gets sort of unwieldy/unreadable.
CGRect newFrame = CGRectMake(0, 0, 500, 500);
UIView *flashView = [[UIView alloc] initWithFrame:newFrame];
flashView.tag = 999;
[flashView setBackgroundColor:[UIColor grayColor]];
[flashView setAlpha:0.f];
[self.view addSubview:flashView];
[UIView animateWithDuration:.2f
animations:^{
// STEP 1: FADE IN
[flashView setAlpha:1.f];
}
completion:^(BOOL finished){
[UIView animateWithDuration:.9f
animations:^{
// STEP 2: FADE OUT
[flashView setAlpha:0.f];
}
completion:^(BOOL finished){
// STEP 3: CLEAN UP
[flashView removeFromSuperview];
}
];
}];

Answer 1

What you're doing is correct. Sometimes the nesting can get ugly. One alternative for readability is to put each animation in its own method:
-(IBAction)someButtonPressed:(id)sender {
[self saveSomeData];
[self fadeInAndOut];
}
-(void)fadeInAndOut {
[UIView animateWithDuration:.2f
animations:^{
// STEP 1: FADE IN
[self.flashView setAlpha:1.f];
}
completion:[self fadeOut]
];
}
-(void (^)(BOOL))fadeOut {
return ^(BOOL finished) {
[UIView animateWithDuration:.9f
animations:^{
// STEP 2: FADE OUT
[self.flashView setAlpha:0.f];
}
completion:[self cleanUpFlashView]
];
};
}
-(void (^)(BOOL))cleanUpFlashView {
return ^(BOOL finished){
// STEP 3: CLEAN UP
[self.flashView removeFromSuperview];
};
}

Answer 2

That way isn't horrible if you're just nesting once with simple code. If you're going to do something more complex you might try animateWithDuration:delay:options:animations:completion:
using delay: as a way to link the animations. For example:
[UIView animateWithDuration:.2f delay:0
options:UIViewAnimationOptionCurveEaseIn|UIViewAnimationOptionAllowUserInteraction
animations:^{
// STEP 1: FADE IN
[flashView setAlpha:1.f];
}
completion:nil
];
[UIView animateWithDuration:.9f delay:.2f
options:UIViewAnimationOptionCurveEaseIn|UIViewAnimationOptionAllowUserInteraction
animations:^{
// STEP 2: FADE OUT
[flashView setAlpha:0.f];
}
completion:^(BOOL finished){
// STEP 3: CLEAN UP
[flashView removeFromSuperview];
}
];