如何在呈现之前设置根视图控制器的属性？

Question

我在 storyboard 中有某个 UINavigationController 我从另一个视图控制器模态呈现：

UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
UINavigationController *myNavController = [storyboard instantiateViewControllerWithIdentifier:@"myNavController"];
[self presentViewController:myNavController animated:YES completion:nil];

此导航控制器已将另一个 UIViewController 设置为其在 storyboard 中的根视图控制器。我想在显示之前为这个根视图控制器设置一些属性，但我试过这个：

UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
UINavigationController *myNavController = [storyboard instantiateViewControllerWithIdentifier:@"myNavController"];
[self presentViewController:myNavController animated:YES completion:nil];
 MyRootViewController *myRootViewController = [storyboard instantiateViewControllerWithIdentifier:@"myRootViewController"];
[myRootViewController setSelectedItem:selectedItem];
[myRootViewController setDelegate:self];

但是当我尝试设置其属性时，根视图控制器似乎尚未加载...

我该怎么做？谢谢

Answer 1

如果你调试过，你会发现MyRootViewController *myRootViewController = [storyboard instantiateViewControllerWithIdentifier:@"myRootViewController"];制作的myRootViewController并不是myNavController真正的rootViewController。

这个方法-instantiateViewControllerWithIdentifier:只是给你一个全新的 UIViewController 实例。

所以，如果你想获得真正的 rootViewController，只需将其替换为以下内容：

UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
UINavigationController *myNavController = [storyboard instantiateViewControllerWithIdentifier:@"myNavController"];

 MyRootViewController *myRootViewController = myNavController.viewControllers[0];
[myRootViewController setSelectedItem:selectedItem];
[myRootViewController setDelegate:self];

[self presentViewController:myNavController animated:YES completion:nil];

如何在呈现之前设置根视图控制器的属性？

How to set properties of a root view controller before being presented?

ios

uinavigationcontroller

segue

presentviewcontroller

rootview