Stopwatch using NSTimer incorrectly includes paused time in display

Question

This is my code for an iPhone stopwatch. It works as expected and stops and resumes when the buttons are clicked.

When I hit \"Stop\", however, the timer won\'t st

Answer 1

A timer class I created in Swift for a timer program in which a counter is updated every second from a set time. Answered to illustrate the Swift solution and the NSTimer function.

The timer can be stopped and restarted; it will resume from where it stopped. Events can be intercepted by the delegate for start, stop, reset, end and second events. Just check the code.

import Foundation

protocol TimerDelegate {
  func didStart()
  func didStop()
  func didReset()
  func didEnd()
  func updateSecond(timeToGo: NSTimeInterval)
}

// Inherit from NSObject to workaround Selector bug
class Timer : NSObject {

  var delegate: TimerDelegate?
  var defaultDuration: NSTimeInterval?

  var isRunning: Bool {
    get {
      return self.timer != nil && timer!.valid
    }
  }

  private var secondsToGo: NSTimeInterval = 0

  private var timer: NSTimer?

  init(defaultDuration: NSTimeInterval, delegate: TimerDelegate? = nil) {
    self.defaultDuration = defaultDuration
    self.delegate = delegate
    super.init()
  }

  func start() {
    self.timer = NSTimer.scheduledTimerWithTimeInterval(1, target: self, selector: "updateTimer", userInfo: nil, repeats: true)
    self.timer!.tolerance = 0.05

    if delegate != nil { delegate!.didStart() }
  }

  func stop () {
    self.timer?.invalidate()
    self.timer = nil

    if delegate != nil { delegate!.didStop() }
  }

  func reset() {
    self.secondsToGo = self.defaultDuration!

    if delegate != nil { delegate!.didReset() }
  }


  func updateTimer() {
    --self.secondsToGo
    if delegate != nil { delegate!.updateSecond(self.secondsToGo) }

    if self.secondsToGo == 0 {
      self.stop()
      if delegate != nil { delegate!.didEnd() }
    }
  }

}