IOS/Objective-c: code reduction within animations - ios

Question

I have this simple animation that fades in several labels, one at a time. But I wonder if it is possible to reduce the code with this logic?
[UIView animateWithDuration:0.50f animations:^{
[_latLabel setAlpha:0.9f];
[_firstLat setAlpha:0.9f];
} completion:^(BOOL finished) {
[UIView animateWithDuration:0.50f animations:^{
[_lonLabel setAlpha:0.9f];
[_firstLon setAlpha:0.9f];
}completion:^(BOOL finished) {
[UIView animateWithDuration:0.50f animations:^{
[_speedLabel setAlpha:0.9f];
[_firstSpeed setAlpha:0.9f];
}completion:^(BOOL finished) {
[UIView animateWithDuration:0.50f animations:^{
[_realNorthLabel setAlpha:0.9f];
[_firstReal setAlpha:0.9f];
}completion:^(BOOL finished) {
[UIView animateWithDuration:0.50f animations:^{
[_magneticNorthLabel setAlpha:0.9f];
[_firstMagnetic setAlpha:0.9f];
}];
}];
}];
}];
}];

Answer 1

Considering the need to perform operation on 2 label objects while executing any single section of the animation block, create a dictionary structure wherein section indexes define the chronological order of the sections animations to be performed & each section index contains an array of label objects.
A simple iterating loop over this structure christened here as dictionaryOfSectionedLabels can help achieve the desired alternate animation implementation.
NSDictionary<NSNumber *, NSArray *> *dictionaryOfSectionedLabels = #{ #0: #[_latLabel, _firstLat],
#1: #[_lonLabel, _firstLon],
#2: #[_speedLabel, _firstSpeed],
#3: #[_realNorthLabel, _firstReal],
#4: #[_magneticNorthLabel, _firstMagnetic]
};
for (NSUInteger i = 0; i < dictionaryOfSectionedLabels.allKeys.count; i++) {
[UIView animateWithDuration:0.5 delay:0.5*i options:UIViewAnimationOptionLayoutSubviews animations:^{
UILabel *firstLabel = [dictionaryOfSectionedLabels[#(i)] firstObject];
UILabel *secondLabel = [dictionaryOfSectionedLabels[#(i)] lastObject];
firstLabel.alpha = 0.9f;
secondLabel.alpha = 0.9f;
} completion:nil];
}

Answer 2

Creating an NSDictionary of your labels can be tedious and confusing code to read in the future. I'd recommend you just create a method.
-(void)customFadeForLabel:(UILabel *)theLabel withDelay:(float)delayAmount {
[UIView animateWithDuration:0.50f
delay:delayAmount
options:UIViewAnimationOptionCurveEaseInOut
animations:^{
[theLabel setAlpha:0.9f];
}completion:nil];
}
Then just call it as needed with delays
[self customFadeForLabel:_latLabel withDelay:0.00f];
[self customFadeForLabel:_firstLat withDelay:0.00f];
[self customFadeForLabel:_lonLabel withDelay:0.50f];
[self customFadeForLabel:_firstLon withDelay:0.50f];
[self customFadeForLabel:_speedLabel withDelay:1.00f];
[self customFadeForLabel:_firstSpeed withDelay:1.00f];
[self customFadeForLabel:_realNorthLabel withDelay:1.50f];
[self customFadeForLabel:_firstReal withDelay:1.50f];
[self customFadeForLabel:_magneticNorthLabel withDelay:2.00f];
[self customFadeForLabel:_firstMagnetic withDelay:2.00f];