iOS Storyboard - 导航 Controller 不工作

Question

我在使用 Storyboard 的 iOS 项目中遇到导航 Controller 问题。

该项目的主要部分是一个UITabBar。当应用程序第一次加载屏幕 RegisterViewController 时:



当用户点击“注册”按钮时，会发出 HTTP POST 请求，然后在收到响应(JSON 对象)后，屏幕 QuestionnaireViewController 会使用:

UIStoryboard *mainStoryboard = [UIStoryboard storyboardWithName:@"MainStoryboard" bundle:nil];

QuestionnaireViewController *questionnaireViewController = [mainStoryboard instantiateViewControllerWithIdentifier:@"QuestionnaireView"];
[questionnaireViewController setModalTransitionStyle:UIModalTransitionStyleCrossDissolve];
[questionnaireViewController setQuestionsAndAnswers:_questionsAndAnswers];

[self presentViewController:questionnaireViewController animated:NO completion:nil];

当用户点击 QuestionnaireViewController 中的单元格时，会向 prepareForSegue:sender 发送一条消息:

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    UINavigationController *navigationController = segue.destinationViewController;

    AnswersViewController *answersViewController = [[navigationController viewControllers] objectAtIndex:0];

    NSIndexPath *indexPath = [self.tableView indexPathForCell:sender];
    NSArray *answers = [[_questionsAndAnswers objectAtIndex:indexPath.row] objectForKey:@"answers"];

    [answersViewController setAnswers:answers];
}

此时应用程序崩溃并出现以下错误:
-[AnswersViewController viewControllers]:发送到实例的无法识别的选择器。

下面是对我的 Storyboard的更全面的概述，这可能有助于理解我哪里出错了:



我很困惑如何解决这个问题，并希望有人能够提供帮助。

谢谢，
缺口

Answer 1

首先，你应该展示导航 Controller ，而不是它的 Root View Controller 。然后当你想用一些数据填充 Root View Controller 时，你需要将它引用为导航 Controller 的 Root View Controller :

UINavigationcontroller *questionnaireNavController = [self.storyboard instantiateViewControllerWithIdentifier:@"QuestionnaireNavigationController"];
[questionnaireNavController setModalTransitionStyle:UIModalTransitionStyleCrossDissolve];
QuestionnaireViewController *qvc = (QuestionnaireViewController *)[questionnaireNavController topViewController];
[qvc setQuestionsAndAnswers:_questionsAndAnswers];

[self presentViewController:questionnaireNavController animated:NO completion:nil];

其次，在 prepareForSegue:sender: 你根本不需要引用导航 Controller :

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    AnswersViewController *answersVC = segue.destinationViewController;
    NSIndexPath *indexPath = [self.tableView indexPathForCell:sender];
    NSArray *answers = [[_questionsAndAnswers objectAtIndex:indexPath.row] objectForKey:@"answers"];

    [answersVC setAnswers:answers];
}