How do I change timing for NSTimer?

You could try adjusting the timer's FireDate, see setFireDate

You can't change the interval at which a timer fires. No way. There's no API for doing this.

Two obvious workarounds: If you always change the interval, then you can just change the next time that the timer fires; this has precedence over the timer interval. Of course you have to do that every time the timer fires. If you sometimes change the interval, just invalidate the first timer and create a new timer with the new interval.

Here is one solution to Hardik's question using NSTimer's fireDate property (written in Swift):

Swift 2

var timeInterval = 0.50
NSTimer.scheduledTimerWithTimeInterval(timeInterval, target: self, selector: Selector("onTimer:"), userInfo: nil, repeats: true)

func onTimer(timer: NSTimer) {
    timeInterval += 0.05
    timer.fireDate = timer.fireDate.dateByAddingTimeInterval(timeInterval)
}

Swift 3, 4, 5

var timeInterval = 0.50
Timer.scheduledTimer(timeInterval: timeInterval, target: self, selector: #selector(self.onTimer), userInfo: nil, repeats: true)

@objc func onTimer(timer: Timer) {
    timeInterval += 0.05
    timer.fireDate = timer.fireDate.addingTimeInterval(timeInterval)
}

Sure you can do this. Change repeats:YES to repeats:NO so that the timer doesn't repeat, and then in onTimer, just start a new timer with a longer interval. You need a variable to hold your interval so that you can make it a bit longer each time through onTimer. Also, you probably don't need to retain the timer anymore, as it will only fire once, and when it does, you'll get a new timer.

I'm no Objective-C expert (or iOS expert...) and it's been a while but I think something like this:

float gap = 0.50;

[NSTimer scheduledTimerWithTimeInterval:gap target:self selector:@selector(onTimer) userInfo:nil repeats:NO];

-(void) onTimer {
    gap = gap + .05;
    [NSTimer scheduledTimerWithTimeInterval:gap target:self selector:@selector(onTimer) userInfo:nil repeats:NO];
}

Something like that? Oh, and I'm really not too sure about the retain semantics here... read the docs to make sure you don't leak!