title: why only viewWillAppear called on navigation back
body: <p>I have doubt need to be clear.. I have stack and a navigation controller.now when the stack loads the <code>viewDidLoad</code> <code>viewWillAppear</code> <code>viewDidAppear</code> will be called. when i click some button then this button push me to the new stack , now new stack gives me the option of the back..now when i click on the back of the navigation controller..why only <code>viewWillAppear</code> will be called ..why not <code>viewDidLoad</code> and not <code>viewDidAppear</code></p>