NavigationBar 返回按鈕

//設置導航返回按鈕  不讓back 出現

let image = UIImage(named: "nav_back")?.withRenderingMode(UIImageRenderingMode.alwaysOriginal)

        (UINavigationBar.appearance()).backIndicatorImage = image

        (UINavigationBar.appearance()).backIndicatorTransitionMaskImage = image

        (UIBarButtonItem.appearance()).setBackButtonTitlePositionAdjustment(UIOffset.init(horizontal: 0, vertical: -60), for: .default)