How to hide iOS status bar

In my iOS video app status bar is hidden in some view controllers. I have done this using following code.

[[UIApplication sharedApplication] setStatusBarHidden:YES];

• It works for iOS 5 and iOS 6 , but not in iOS 7.

• I tried with this in particular view controller,

Eg:

-(BOOL)prefersStatusBarHidden { return YES; }

It works well, but I cant show status bar again in the parent view controller.