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swiftxcodestopwatch

Create a stopwatch in Swift using .timeIntervalSince()

I need to create a simple stopwatch in Swift using the method timeIntervalSince(). I don't really understand how to use timeIntervalSince (what I need and how to implement it) and how to transform it into a String that will show me the passed time like "00:00:00".

I know I need to use a Timer to update the Label and invalidate it when clicking on "Stop".

I'd really appreciate any help on this. Let me know if you need more information.

Solution

  • The method timeIntervalSince(_:) is a method of Date. It gives you the number of seconds that have passes since some other date and the date you are asking.

    So,

    Create a StopwatchVC. Give StopwatchVC a startTime var of type Date. Also give it a Timer var. Lets call that updateTimer.

    When the user taps the start button, save Date() (the time right now) into startTime. Also start a repeating timer, updateTimer that fires every 1/10 second. (or however often you want to update your stopwatch, but note that faster than 1/60 is pointless because the screen can't update any faster than that, and timers are only accurate to about 1/50 sec anyway.)

    Each time updateTimer fires, calculate the number of seconds that have elapsed since the start time and display it to the screen:

    let seconds = Date().timeIntervalSince(startTime)

    Date() is the current date and time, with sub-millisecond accuracy. Date().timeIntervalSince(startTime) will give you the number of seconds since startTime, again with sub-millisecond accuracy.

    Format and display the elapsed time to the screen. You could use a DateComponentsFormatter or build a time string yourself using a NumberFormatter, or even String(format:)