Quickies for NSTimer

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General

• Basics [permalink]
  

  - (void) handleTimer: (NSTimer *) timer
  {
      do some work here...
  } // handleTimer
  
  NSTimer *timer;
  
  timer = [NSTimer scheduledTimerWithTimeInterval: 0.5
                   target: self
                   selector: @selector(handleTimer:)
                   userInfo: nil
                   repeats: YES];
  

• NSTimers and NSTerminateLater [permalink]
  If your application has an open TCP connection to a server and you receive an applicationShouldTerminate: message, you're likely to want to returnNSTerminateLater so that you can first gracefully shut down the connection before quitting.

  There is a gotcha: returning NSTerminateLater stops the main runloop, so your NSTimers will stop working from that point on. Thus, if you were depending on a timer firing to finish up your shut-down process, you'll never see it, and you'll hang. The solution is to return NSTerminateCancel, then do whatever you need to do and then terminate yourself manually. (Thanks to Larry Gerndt for this one!)

Swift

• Using NSTimer [permalink]
  

      var sessionTimer: NSTimer?
  
  ...
          sessionTimer = 
              NSTimer.scheduledTimerWithTimeInterval(0.5, target: self, 
                                                     selector: #selector(SessionEditorViewController.lubDub(_:)), 
                                                     userInfo: nil, repeats: true)
  ...
  
      func lubDub(timer: NSTimer) {
          let elapsedTime = NSDate().timeIntervalSince1970 - startTime
          print("(elapsedTime)")
      }
  ...
  
      // clean up when done
          sessionTimer?.invalidate()
          sessionTimer = nil
  

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