Objective C : NStimer- How to stop timer after n hours - objective-c

Question

I have started the timer using below call, and need to stop it after n hours
self.timer = [NSTimer scheduledTimerWithTimeInterval:20 target:self selector:#selector(sendLocationUpdates) userInfo:nil repeats:YES];
The solution I can thin of get the current time when timer start and keep adding time till threshold reaches. Or is there any better way to stop timer?

Answer 1

Add an instance variable to the class to store the start time of the timer:
YourClass.m:
#interface YourClass () {
NSTimeInterval _startTime;
}
#end
Record the current time when creating the timer:
self.timer = [NSTimer scheduledTimerWithTimeInterval:20 target:self selector:#selector(sendLocationUpdates) userInfo:nil repeats:YES];
_startTime = [NSDate timeIntervalSinceReferenceDate];
and test the current time in the sendLocationUpdates method:
#define TIMER_LIFE_IN_SECONDS 3000.0
- (void)sendLocationUpdates
{
// do thing
NSTimeInterval now = [NSDate timeIntervalSinceReferenceDate];
if (now - _startTime > TIMER_LIFE_IN_SECONDS) {
[self.timer invalidate];
self.timer = nil;
}
}

Answer 2

simple solution
declare two properties
#property NSInteger counter;
#property NSTimeInterval interval;
set the counter to 0 before starting the timer
self.counter = 0;
self.interval = 20.0;
self.timer = [NSTimer scheduledTimerWithTimeInterval:self.interval target:self selector:#selector(sendLocationUpdates) userInfo:nil repeats:YES];
in the sendLocationUpdates method increment the counter
- (void)sendLocationUpdates
{
counter++;
if (counter == 4 * (3600 / self.interval)) {
[self.timer invalidate];
self.timer = nil;
}
// do other stuff
}
with a given time interval of 20 seconds the timer fires 180 times per hour.
In the example the timer stops after 4 hours