iOS: Counting upwards animation - ios

Question

I want to animate my UILabel such that it looks like its counting upward. For arguments sake lets just say I want it to go up by 1 every second.
None of the ways below worked properly.
A simple for loop (example here) doesn't work because its way too fast.
for(int i =0;i<1000;i++)
{
lblNum.text = [NSString stringWithFormat:#"%d",i];
}
Adding in sleep(1) doesn't work because the executions are asynchronous (I think thats why at least)
I also tried:
for(int i=0;i<1000;i++)
{
[self performSelector:#selector(updateLbl:)
withObject:[NSNumber numberWithInt:i ] afterDelay:1];
}
-(void)updateLbl:(NSNumber *)num
{
lblNum.text = [NSString stringWithFormat:#"%#",num];
}
As well as:
for(int i=0;i<1000;i++)
{
dispatch_async(dispatch_get_global_queue( DISPATCH_QUEUE_PRIORITY_LOW, 0), ^{
// Do something...
sleep(1);
dispatch_async(dispatch_get_main_queue(), ^{
lblNum.text = [NSString stringWithFormat:#"%d",i];
});
});
}

Answer 1

NSTimer *timer = [NSTimer scheduleTimerWithTimeInterval:1.0 target:self selector:#selector(increment:) userInfo:label repeats:YES];
...
- (void)increment:(NSTimer *)timer {
UILabel *label = (UILabel *)timer.userInfo;
NSInteger i = label.text.integerValue;
i++;
label.text = [NSString stringWithFormat:#"%d", i];
if(someCondition){
[timer invalidate]//stops calling this method
}
}

Answer 2

I think a good way to do this is to use an NSTimer.
How do I use NSTimer?
The implementation is simple, just set repeat to YES and make the timer fire every second. You could have a variable keep track of count and increase it each time.
A good rule of thumb for programming: Never use sleep!!

Answer 3

Use NSTimer & NSRunLoop to perform animation in your code
timer_=[NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:#selector(labelAnimation:) userInfo:nil repeats:NO];
[[NSRunLoop currentRunLoop] addTimer:timer_ forMode:NSDefaultRunLoopMode];
- (void)increment:(NSTimer *)timer
{
if(isAnimationComplete)
{
[timer_ invalidate]//stops calling this method
}
else
{
//perform your action
}
}