有没有办法找出视图控制器是否从导航堆栈中弹出？

Question

我试图检测视图控制器何时从导航堆栈中弹出，以某种方式我在堆栈的下一层有对控制器的引用（当前使用 Swift 3）。谢谢

Answer 1

UINavigationController 有一个属性viewControllers，其中包含当前在堆栈上的视图控制器数组。您可以获取视图控制器数组，然后从该数组中获取倒数第二个视图控制器：

guard let navController = self.navigationController else {
  print("We are not part of a navigation stack!")
  return
}
let stack = navController.viewControllers
let stackCount = stackCount
if stackCount > 1 {
  let nextVC = viewControllers[stackCount - 2]
  //nextVC now contains the view controller one down from the current VC
} else {
  //We are the root view controller
}