Count Down Timer in iPhone

Question

I have two time.. one fetched directly as string(@"21:00") and other is the current time. I want to display a count down timer showing how much time left from now to reach 21:00.

For eg: the label i use should display "You have 3hrs and 30 minutes left.." if the current time is 17:30. thanks..

Answer 1

OK have completely revised my answer, and have created a complete solution to the problem, with fully tested sample code available on github.

Enjoy :)

Answer 2

Something like this should do it. This will give you the remaining time in seconds. Then you just need to to standard timer stuff as indicated in other answers.

//assumption: targetTime is after now
NSString *targetTime = @"21:00";

//split our time into components
NSArray *timeSplit = [targetTime componentsSeparatedByString:@":"];

NSUInteger hours =  [[timeSplit objectAtIndex:0] intValue];
NSUInteger minutes =  [[timeSplit objectAtIndex:1] intValue];

NSDate *now = [NSDate date];

//split now into year month day components
NSCalendar *currentCalendar = [NSCalendar currentCalendar];
NSDateComponents *dateComponents = [currentCalendar components:NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit fromDate:now];

//set our time components from above
[dateComponents setHour:hours];
[dateComponents setMinute:minutes];

NSDate *targetDate = [currentCalendar dateFromComponents:dateComponents];

//ensure target is after now
if ([targetDate timeIntervalSinceDate:now] < 0)
{
    NSDateComponents *day = [[NSDateComponents alloc] init];
    [day setDay:1];

    targetDate = [currentCalendar dateByAddingComponents:day toDate:targetDate options:0]; 
}

NSTimeInterval timeRemaining = [targetDate timeIntervalSinceDate:now];