Optimise a function that calls itself in Obj C - objective-c

Question

I've written a function that checks whether a live score has changed every 0.1 seconds, and if it has it plays a system sound on iPhone.
- (void) checkIfShouldHaptic {
loadedScore = [self loadScoreFromKey:keyScore]; //load score saved in key
controllerScore = [self checkCurrentScore]; //check current score
if (loadedScore < controllerScore){ //if score in key is less than controller score
[self saveScore:controllerScore]; //save new score in key
AudioServicesPlaySystemSound(kSystemSoundID_Vibrate); //play system sound
[self repeatCheckIfShouldHaptic]; //repeat
}
else { //else score is not less
[self repeatCheckIfShouldHaptic]; //repeat
}
}
- (void)repeatCheckIfShouldHaptic {
[NSTimer scheduledTimerWithTimeInterval:timeDelayInSeconds target:self selector:#selector(checkIfShouldHaptic) userInfo:nil repeats:NO];
}
My programming capabilities are pretty limited so I was wondering if someone could show me if and how this could be optimised?
I'm not sure if a function calling itself over and over is good practice or if there's a better way to repeat a check.
Thank you.

Answer 1

I think you can use KVO
#property NSUInteger score;
- (void)viewDidLoad
{
[super viewDidLoad];
[self addObserver:self forKeyPath:#"score" options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld context:nil];
}
-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
NSLog(#"From KVO");
if([keyPath isEqualToString:#"score"])
{
id oldScore = [change objectForKey:NSKeyValueChangeOldKey];
id newScore = [change objectForKey:NSKeyValueChangeNewKey];
NSLog(#"%# %#", oldScore, newScore);
}
}

Answer 2

I would rewrite your code a little. IMHO Using NSTimer is more resources consuming operation then using GCD.
Your approach is not so bad if you don't have any other options to receive some sort of notification.
- (void)checkIfShouldHaptic {
loadedScore = [self loadScoreFromKey:keyScore]; //load score saved in key
controllerScore = [self checkCurrentScore]; //check current score
if (loadedScore < controllerScore){ //if score in key is less than controller score
[self saveScore:controllerScore]; //save new score in key
AudioServicesPlaySystemSound(kSystemSoundID_Vibrate); //play system sound
}
[self repeatCheckIfShouldHaptic]; //repeat
}
- (void)repeatCheckIfShouldHaptic {
__weak typeof(self) weakSelf = self;
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(timeDelayInSeconds * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
[weakSelf checkIfShouldHaptic]
});
}