Reducing a NSNumber by itself-1, automatically - ios

Question

Ok so basically, I'm trying to build some code that allows an NSNumber to reduce by 1 every minute,
This is what I have so far.
- (void)viewDidLoad {
[super viewDidLoad];
NSNumber *numVar = [NSNumber numberWithUnsignedChar:99];
[self num];
}
-(void)num{
usleep(60000000);
NSNumber *numVar = [NSNumber numberWithUnsignedChar:numVar-1];
[self num];
}
First off, it won't reduce by one every minute and secondly is it wrong to have the initial numVar in viewDidLoad?

Answer 1

We tried this and it worked fine for what we needed :
You need to re-arrange this in your code though
- (void)viewDidLoad{
NSTimer *timer;
int minutes = 0;
//Creating a label that shows the timer ; i assume you have one that is already linked
_labelTimer.text = [NSString stringWithFormat:#"This is %i minute", minutes];
//Creating the timer itself with the NSTimer object
timer = [NSTimer scheduledTimerWithTimeInterval: 60.0 target: self selector:#selector(decreaseTimeCount) userInfo:nil repeats:YES];
//Note that 60 is the number of seconds before it calls the selector. You can use 1 if you want it to change your timer/clock every second
}
- (void)decreaseTimeCount{
//The method changes the value of my variable and updates the label. If i'm at the 10th minute, i could do something, like perform a segue.
minute+=1;
_labTimer.text = [NSString stringWithFormat:#"This is %i minutes", minutes];
if (minutes == 10){
//do stuff
}
}

Answer 2

You sleep inside the main thread, blocking your UI. You need to use an NSTimer or similar timing mechanism to run the function periodically without blocking.

Answer 3

#implementation YourViewController
{
NSNumber *numVar;
}
- (void)viewDidLoad
{
[super viewDidLoad];
numVar = [NSNumber numberWithUnsignedChar:99];
[NSTimer scheduledTimerWithTimeInterval:60 target:self selector:#selector(timerFireMethod:) userInfo:nil repeats:YES];
}
- (void)timerFireMethod:(NSTimer *)timer
{
numVar = [NSNumber numberWithInt:[numVar intValue] - 1];
}

Answer 4

Whenever I need something fast I do it like this
- (void)viewDidLoad
{
[super viewDidLoad];
[self performSelector:#selector(num) withObject:nil afterDelay:60];
}
- (void)num
{
NSNumber *numVar = [NSNumber numberWithUnsignedChar:numVar-1];
[self performSelector:#selector(num) withObject:nil afterDelay:60];
}
And you can decide in the num function wheather you want to do it again after a minute or not.