无法导航到iOS 9中的其他屏幕

Question

我从第二个屏幕导航到第三个屏幕，但它显示错误应用程序试图在目标上推送一个nil视图控制器。以下是用于导航的代码，

 if (appDelegate.thirdViewController == nil) {
    ThirdViewController *sThirdViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"ThirdViewController"];
    [appDelegate setThirdViewController:sThirdViewController];
}

[self.navigationController pushViewController:appDelegate.thirdViewController animated:YES];

Answer 1

似乎AppDelegate没有参考，

你写了appDelegate =（AppDelegate *）[[UIApplication sharedApplication] delegate];

检查一次..