UILabel not hidden when set to Hidden - ios

Question

My app receives a measurement every minute. When the measurement is 0, I want a label to be displayed in the middle. When it is greater than that, when I want the label to disappear. The issue I have is that once the label appears, it doesn't hide once I set its hidden mode to true.
UILabel *emptyBagLabel = [[UILabel alloc] init];
emptyBagLabel.textAlignment = NSTextAlignmentCenter;
emptyBagLabel.textColor = [UIColor darkGrayColor];
emptyBagLabel.numberOfLines = 0;
emptyBagLabel.text = #"EMPTY POUCH";
emptyBagLabel.translatesAutoresizingMaskIntoConstraints = NO;
emptyBagLabel.hidden = true;
[self addSubview:emptyBagLabel];
[emptyBagLabel.centerXAnchor constraintEqualToAnchor:self.centerXAnchor].active = YES;
[emptyBagLabel.centerYAnchor constraintEqualToAnchor:self.centerYAnchor].active = YES;
[emptyBagLabel.widthAnchor constraintEqualToAnchor:self.widthAnchor].active = YES;
[emptyBagLabel.heightAnchor constraintEqualToConstant:100].active= YES;
if (measurement == 0 || measurement <= 0.005) {
emptyBagLabel.hidden = false;
}
if (measurement > 0.005) {
emptyBagLabel.hidden = true;
}
I've been scratching my head at this for a while, a bit frustrated with how I'm not able to solve such a trivial issue. The method I have it in is called every minute. I know the method and the hidden = true line are getting called, so I'm unsure as to what is causing the issue.

Answer 1

Subview that are added programmatically ought to be added lazily, so you get exactly one subview instance. I'd refactor the code like this...
- (UILabel *)emptyBagLabel {
UILabel *emptyBagLabel = (UILabel *)[self.view viewWithTag:128];
if (!emptyBagLabel) {
emptyBagLabel = [[UILabel alloc] init];
emptyBagLabel.tag = 128;
// set all of the attributes her for how the label looks, textColor, etc.
// everything except the properties that change over time
[self addSubview:emptyBagLabel];
}
return emptyBagLabel;
}
// if this view is built using initWithFrame...
- (id)initWithFrame:(CGRect)frame {
self = [super initWithFrame:frame];
if (self) {
[self emptyBagLabel]; // to add the label initially
}
return self;
}
// if this view is ever loaded from a nib, then
- (id)initWithCoder:(NSCoder *)aDecoder {
self = [super initWithCoder:aDecoder];
if (self) {
[self emptyBagLabel];
}
return self;
}
// elsewhere in the view, when you get the measurement
// side note: alpha is usually a better choice than hidden because you can animate it
if (measurement == 0 || measurement <= 0.005) {
self.emptyBagLabel.alpha = 1.0;
}
if (measurement > 0.005) {
self.emptyBagLabel.alpha = 0.0;
}