title: Saved data lost after kill app using NSUserDefaults
body: <p>I use NSUserDefaults in my setting. App works well even I press home key let app into background, but if I kill the app, the data save in NSUserDefaults will lost. Here is my code. I have use synchronize.
  The First initialize:</p>
  
  <pre><code> if (![userDefaults integerForKey:
            kORFootageAirPlayModeKey])
      {
          [userDefaults setInteger:TRUE forKey:kORFootageAirPlayModeKey];
      }
      [userDefaults synchronize];
  </code></pre>
  
  <p>Read value out in a viewController:</p>
  
  <pre><code>airPlayMode = [[NSUserDefaults standardUserDefaults]integerForKey:kORFootageAirPlayModeKey];
  </code></pre>
  
  <p>Set it in a action:</p>
  
  <pre><code>- (IBAction)changeAirPlayStatus:(id)sender
  {
  
      if (sender)
      {
          airPlayMode = [sender tag];
  
          [[NSUserDefaults standardUserDefaults] setInteger:airPlayMode forKey:kORFootageAirPlayModeKey];
          [[NSUserDefaults standardUserDefaults] synchronize];
      }
  .....
  </code></pre>
  
  <p>}</p>