Why is my NSNotification its observer called multiple times?

Question

Within an App I make use of several viewcontrollers. On one viewcontroller an observer is initialized as follows:

[[NSNotificationCenter defaultCenter] remov         


        

Answer 1

Ran into this issue in an application running swift. The application got the notification once when first launched. the notification increases the number of times you go into the background and come back. i.e

• app launches one - add observer gets gets called once in view will appear or view did load - notification is called once
• app goes into background and comes back, add observer gets called again in view will appear or view did load. notification gets called twice.
• the number increases the number of times you go into background and come back.
• code in view will disappear will make no difference as the view is still in the window stack and has not been removed from it.

solution: observe application will resign active in your view controller:

  NSNotificationCenter.defaultCenter().addObserver(self, selector: "applicationWillResign:", name: UIApplicationWillResignActiveNotification, object: nil)

  func applicationWillResign(notification : NSNotification) {
    NSNotificationCenter.defaultCenter().removeObserver(self)
  }

this will make sure that your view controller will remove the observer for the notification when the view goes into background.