Check out example codes for "hide status bar ios". It will help you in understanding the concepts better.

Code Example 1

override func viewWillAppear(animated: Bool) {
    super.viewWillAppear(animated)
    UIApplication.sharedApplication().setStatusBarHidden(true, withAnimation: UIStatusBarAnimation.None)
}

override func viewWillDisappear(animated: Bool) {
    super.viewWillDisappear(animated)
    UIApplication.sharedApplication().setStatusBarHidden(false, withAnimation: UIStatusBarAnimation.None)
}

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