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我读过很多类似的帖子，但两天后，我想我应该问自己的问题。

我有一个单独的 CoreData 控制器。这会将实体对象从 AppDelegate 很好地传递到 RootViewController。它不会将它传递给特定的（类别）视图控制器，我不知道为什么。

我尝试传递对象的 App Delegate 中的代码是这样的：

rootViewController.managedObjectContext = self.coreDataController.mainThreadContext;
    categoryListViewController.managedObjectContext = self.coreDataController.mainThreadContext;
    NSLog(@"AD/core data controller is %@", coreDataController.mainThreadContext);
    NSLog(@"AD- rootVC is %@", rootViewController.managedObjectContext);
    NSLog(@"AD/category list is %@", categoryListViewController.managedObjectContext);

并且日志显示核心数据控制器和根 vc 被填充，但类别 vc 没有。

2012-12-02 14:28:33.187 [50351:907] AD/coredatacontroller moc is <NSManagedObjectContext: 0x21065160>
2012-12-02 14:28:33.188 [50351:907] AD/categorycontroller moc is (null)
2012-12-02 14:28:33.190 [50351:907] AD- rootVC moc is <NSManagedObjectContext: 0x21065160>

任何想法为什么？

更新

如果我按照 Valentin 的建议进行操作，并在 App Delegate 中初始化 Category VC，那么我肯定会通过托管对象，因为我从 Detail VC 调用视图。当我这样做时，我收到错误“应用程序试图在目标上推送一个 nil 视图控制器”。

如果我尝试在详细信息 VC 中初始化类别 VC（并加载上下文），它不会传达，并且日志显示上下文为零。

初始化 VC（在 App Delegate 中）：

categoryListViewController = [[CategoryListViewController alloc] initWithNibName:@"CategoryList-iPad" bundle:nil];

                        // we have loaded from our xib, so has our CoreDataController,
    // so connect as its delegate and setup its persistent store
    //
    self.coreDataController.delegate = self;
    [self.coreDataController loadPersistentStores];



    UINavigationController *rootNavigationController = [[UINavigationController alloc] initWithRootViewController:rootViewController];
    UINavigationController *detailNavigationController = [[UINavigationController alloc] initWithRootViewController:detailViewController];



    // Set up MASTER and DETAIL delegation so we can send messages between views
    rootViewController.detailViewController = detailViewController;
    detailViewController.rootViewController = rootViewController;

    splitViewController = [[UISplitViewController alloc] init];

    splitViewController.viewControllers = @[rootNavigationController, detailNavigationController];
    [[UIDevice currentDevice] beginGeneratingDeviceOrientationNotifications];

    splitViewController.delegate = detailViewController;

    rootViewController.managedObjectContext = self.coreDataController.mainThreadContext;
    categoryListViewController.managedObjectContext = self.coreDataController.mainThreadContext;


    NSLog(@"AD - coreDataController is %@", coreDataController.mainThreadContext);
    NSLog(@"AD - rootViewController is %@", rootViewController.managedObjectContext);
    NSLog(@"AD - categoryListVC is %@", categoryListViewController.managedObjectContext);

调用视图（在 DetailViewController 中）：

 -(void)categoryButtonTapped {
     NSLog(@"%s", __FUNCTION__);

     //categoryListViewController = [[CategoryListViewController alloc] initWithNibName:@"CategoryList-iPad" bundle:nil];
     //categoryListViewController.managedObjectContext = coreDataController.mainThreadContext;
     //categoryListViewController.managedObjectContext = self.coreDataController.mainThreadContext;

 UINavigationController *nc = [[UINavigationController alloc] initWithRootViewController:categoryListViewController];
     nc.modalPresentationStyle = UIModalPresentationFormSheet;


      NSLog(@"DVC FRC is %@", self);
      NSLog(@"DVC FRC/moc is %@", coreDataController.mainThreadContext);
      NSLog(@"DVC FRC/self.moc is %@", self.coreDataController.mainThreadContext);

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

     //[self.navigationController pushViewController:categoryListViewController animated:YES];
}
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1 回答 1

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很可能你的categoryListViewController也是 nil 。尝试查看它是否正确分配/初始化。

于 2012-12-02T19:46:39.147 回答