Question

I have a timer that I start and stop multiple times. How do I accumulate the values once the timer has stopped each time?

Answer 1

When the timer is started note the start time. Whenever the timer fires add the difference between the current time and the start time to your total. Then reset the start time to the current time. When the timer is stopped, you either add the difference between the current time and start time to the total or don’t depending on your application, but you don’t reset the start time. When the timer is restarted, don’t add anything to the total, but reset the start time.

So something like this:

startTime = [[NSDate alloc] initWithTimeIntervalSinceNow]; // This is an NSDate* in your class

Then when your timer fires:

NSDate* currentTime = [NSDate dateWithTimeIntervalSinceNow];
accumulatedTime += [currentTime timeIntervalSinceDate:startTime]; // accumulatedTime is an NSTimeInterval in your class
[startTime release];
startTime = [currentTime retain];

etc.