title: Apply blur effect to a view before presenting on IOS 7/8?
body: <p>im working on an app involving privacy, and i would like to blur the main screen when app starts (then I ask for local authentication etc..)</p>
  
  <p>The main problem i'm having, is that i don't know how to access the view before it is displayed. 
  If i try to get the view inside <code>- (void)viewDidLoad</code> then blur effect is not applied (since the view doesn't exist yet) and if i try to access the view inside <code>- (void)viewDidAppear:(BOOL)animated</code> then the non-blurred view appears for a second before the blur effect is applied.</p>
  
  <p>There is a way to get the view and apply the blur effect before it is displayed on screen?</p>
  
  <p>The code im using for applying the blur effect is:</p>
  
  <pre><code>UIVisualEffect *blurEffect = [UIBlurEffect effectWithStyle:UIBlurEffectStyleExtraLight];
  UIVisualEffectView * visualEffectView = [[UIVisualEffectView alloc] initWithEffect:blurEffect];
  visualEffectView.frame = self.view.window.bounds;
  [UIApplication.sharedApplication.keyWindow.subviews.lastObject addSubview:visualEffectView];
  </code></pre>
  
  <p>Thanks in advance.</p>