ios - 将 managedObjectContext 发送到 viewController 崩溃

Question

我正在尝试通过 segue 将我的 managedObjectContext 从我的 masterViewController 发送到另一个 Controller ，但我总是收到此错误:

-[UINavigationController setManagedObjectContext:]: unrecognized selector sent to instance 0x8d67c70
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[UINavigationController setManagedObjectContext:]: unrecognized selector sent to instance 0x8d67c70'

我在 masterViewController 的 viewDidLoad() 中从我的 appDelegate 获取 managedObjectContext，如下所示:

AppDelegate *appDelegate = [UIApplication sharedApplication].delegate;
self.managedObjectContext = appDelegate.managedObjectContext;

我再也想不出我可能做错了什么，请帮忙。

Answer 1

我猜测具有 managedObjectContext 属性的 View Controller 嵌入在导航 Controller 中。在 segue 方法中，确保获取对正确 View Controller 的引用:

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([[segue identifier] isEqualToString:@"MySegue"]) {

        UINavigationController *navController = (UINavigationController *)segue.destinationViewController;
        MyViewController *vc = (MyViewController *)navController.topViewController;

        AppDelegate *appDelegate = [UIApplication sharedApplication].delegate;
        vc.managedObjectContext = appDelegate.managedObjectContext;
    }
}