prepareForSegue和代表 [英] prepareForSegue and delegates

问题描述

我有一个两个版本的应用程序。在其中一个区段中，当前视图控制器成为一个委托，另一个不是。

   - （void）prepareForSegue：（UIStoryboardSegue *）segue sender：（id）sender 
 {
 if（[segue.identifier isEqualToString：@MoreOptions]）{
 UINavigationController * navigationController = segue.destinationViewController; 
 MoreOptionsViewController * controller =（MoreOptionsViewController *）navigationController.topViewController; 
 controller.delegate = self; 
} else if（[segue.identifier isEqualToString：@FullStoryView]）{
 SingleStoryViewController * detailViewController = segue.destinationViewController; 
 detailViewController.urlObject = sender; 
} 
} 
  

所有这一切都正常，但我想尝试更好地了解代码。我不明白的是，我必须通过从navigationController.topViewController获取参考，而不是像在第二个if条件中那样从segue.destinationViewController中获取它，从而获得对MoreOptionsViewController的引用。是因为我将当前视图控制器（self）设置为代理？再次，我不是想解决问题，只是想更好地了解发生了什么。

解决方案

看看你的故事板，应该明白为什么会这样。您在 UINavigationController 中嵌入了 MoreOptionsViewController ，并将其连接到导航控制器，从而使其成为 destinationViewController 。这是很常见的。

I have an application with two segues. In one of the segues, the current view controller becomes a delegate and the other does not.

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([segue.identifier isEqualToString:@"MoreOptions"]) {
        UINavigationController *navigationController = segue.destinationViewController;
        MoreOptionsViewController *controller = (MoreOptionsViewController *)navigationController.topViewController;
        controller.delegate = self;
    } else if ([segue.identifier isEqualToString:@"FullStoryView"]) {
        SingleStoryViewController *detailViewController = segue.destinationViewController;
        detailViewController.urlObject = sender;
    }
}

All of this is working fine, but I would like to try and understand the code better. What I don't understand is that I have to get a reference to the MoreOptionsViewController by grabbing it from navigationController.topViewController rather than simply getting it from segue.destinationViewController like I do in the second if condition. Is it because I'm setting the current view controller (self) as the delegate? Again, I'm not trying to solve a problem, just trying to get a better understanding of what's going on.

解决方案

Take a look at your storyboard and it should be evident why this is the case. You have embedded MoreOptionsViewController in a UINavigationController and connected a segue to the navigation controller, thus making it the destinationViewController. This is fairly common.

这篇关于prepareForSegue和代表的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！