Timer won't stop after 45 minutes - ios

Question

I have this NSTimer that I want it to stop after 45 minutes, but it won't stop.
What am I doing wrong?
TIMER_COUNT = 45
HOURS_IN_HOURS = 60
HOURS_IN_DAY = 24
- (void)start
{
self.timerCountdown = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:#selector(updateCountdown) userInfo:nil repeats: YES];
}
- (void)stop
{
[self.timerCountdown invalidate];
self.timerCountdown = nil;
}
- (void)updateCountdown
{
NSDate *currentDate = [NSDate date];
NSDate *finalTime = [currentDate dateByAddingTimeInterval:(TIMER_COUNT * HOURS_IN_HOUR)];
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *componentsHours = [calendar components:NSHourCalendarUnit fromDate:currentDate];
NSDateComponents *componentMinuts = [calendar components:NSMinuteCalendarUnit fromDate:currentDate];
NSDateComponents *componentSeconds = [calendar components:NSSecondCalendarUnit fromDate:currentDate];
NSCalendar *gregorianCalendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *componentsDaysDiff = [gregorianCalendar components:NSDayCalendarUnit
fromDate:currentDate
toDate:finalTime
options:0];
NSLog(#"%20d Days, %02d Hours, %02d Minutes, %02d Seconds.", componentsDaysDiff.day, HOURS_IN_DAY - componentsHours.hour, HOURS_IN_HOUR - componentMinuts.minute, HOURS_IN_HOUR - componentSeconds.second);
if ([currentDate compare:finalTime] == NSOrderedSame)
{
NSLog(#"Done.");
[self stop];
}
}
Thanks in advance.

Answer 1

Because your currentDate will keep being set every time your timer ticks. [NSDate date] will set currentDate to the current time every time the updateCountdown method runs. Therefore will finalTime always be 45 minutes ahead of currentDate. You should create a startDate property and set it in the start method instead:
- (void)start
{
self.timerCountdown = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:#selector(updateCountdown) userInfo:nil repeats: YES];
self.startDate = [NSDate date];
}
Then check on the property in the updateCountdown method:
if ([self.startDate compare:finalTime] == NSOrderedSame)
{
NSLog(#"Done.");
[self stop];
}
Alternatively you can use an integer with the number of ticks you are expecting and then substract one from the integer everytime the timer ticks.
Something like this:
- (void)start
{
self.timerCountdown = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:#selector(updateCountdown) userInfo:nil repeats:YES];
self.countdown = TIMER_COUNT * HOURS_IN_HOUR;
}
- (void)updateCountdown
{
self.countdown--;
//your code
if (self.countdown == 0)
{
NSLog(#"Done.");
[self stop];
}
}

Answer 2

- (void)start {
NSString *startTime = [NSDate date];
NSDateComponents *durationComponents = [[[NSDateComponents alloc] init] autorelease];
durationComponents.minutes = 45;
NSCalendar *gregorianCalendar = [NSCalendar currentCalendar];
self.endTime = [calendar dateByAddingComponents:durationComponents
toDate:startTime
options:0];
self.timerCountdown = [NSTimer scheduledTimerWithTimeInterval:1.0
target:self
selector:#selector(updateCountdown)
userInfo:nil
repeats:YES];
}
- (void)stop {
[self.timerCountdown invalidate];
self.timerCountdown = nil;
}
- (void)updateCountdown {
NSDate *currentTime = [NSDate date];
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *currentTimeComponents = [calendar components:(NSHourCalendarUnit | NSMinuteCalendarUnit |NSSecondCalendarUnit)
fromDate:currentTime];
if ([currentTime compare:self.endTime] == NSOrderedDescending) {
[self stop];
}
}

Answer 3

You don't need the startDate property.
And you should not check dates for equality. That is very unlikely to happen.
Use that comparison:
if ([finalTime compare:[NSDate date]] == NSOrderedAscending)
{
NSLog(#"Done.");
[self.timerCountdown invalidate];
[self stop];
}
This means that finalTime is earlier in time than current time.