Isn't LeftBarButtonItem showing on navigation bar?

If you manually create a parent and child relationship between two view controllers, the child view controller might not have a navigation bar in this case. So you might be wondered why the navigation item of the child view controller doesn’t effect on the navigation bar. But you need to understand that the navigation bar on the child view controller is not the child view controller’s navigation bar. Because the child view controller is embedded into the parent view controller. So you need to create a LeftBarButtonItem on the parent’s navigation bar and customize the button with a target and an action pattern in the parent view controller.