On Jul 19, 2008, at 12:41 PM, Eric Lee wrote:
I'm planning on making a stopwatch where the timer fires and then the text field updates by each second.I read online that I should use NSTimeInterval for this, as well as NSDate, and NSTimer.My main question is, how do you use NSTimeInterval?
NSTimeInterval isn't an object, it is a scalar type. Specifically:
typedef double NSTimeInterval;
A double; integral part is # of seconds and fractional part is # of
nths of a second.
Typically, you would create a start time: NSTimeInterval startTime = [NSDate timeIntervalSinceReferenceDate]; And then grab an endTime when you are done: NSTimeInterval endTime = [NSDate timeIntervalSinceReferenceDate]; And calculate an elapsed time: NSTimeInterval elapsedTime = endTime - startTime;Obviously, these variables should be instance variables or otherwise persisted beyond a local scope.
In any case, you use the time intervals and - timeIntervalSinceReferenceDate to keep track of the actual elapsed time. The NSTimer is used to update UI. You don't want to do any interval calculations based when the timer fires as timers are inaccurate. However, you can grab the elapsed time in the timer's fired method via -timeIntervalSinceReferenceDate and calculate based upon that.
b.bum
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