NSManagedObjectContextDidSaveNotification在iOS 7中未触发 [英] NSManagedObjectContextDidSaveNotification not triggered in iOS 7

问题描述

我有一个情况，我对主线程中的NSManagedObject的属性进行一些更改。它属于应用程序的主ManagedObjectContext。

我的应用程序启用了线程下载数据，每个线程都有自己的ManagedObjectContext从单个最近的状态创建PersistentStore。

我正在实现 NSManagedObjectContextDidSaveNotification ，以便MOC中的任何更改都合并回主线程的MOC。下面是它的代码：

   - （void）backgroundMOCDidSave：（NSNotification *）notification 
 {
 //可能的修复：http://stackoverflow.com/questions/3446983/collection-was-mutated-while-being-enumerated-on-executefetchrequest 
 if（！[NSThread isMainThread]）
 {
 [self performSelectorOnMainThread：@selector（backgroundMOCDidSave :) withObject：notification waitUntilDone：YES]; 
 return; 
} 
 
 //我们合并主moc中的背景moc更改
 [self.managedObjectContext mergeChangesFromContextDidSaveNotification：notification]; 
} 
  

注册此通知：

  [[NSNotificationCenter defaultCenter] addObserver：self 
 selector：@selector（backgroundMOCDidSave :) 
 name：NSManagedObjectContextDidSaveNotification 
 object：nil]; 
  

然而，奇怪的事情发生在iOS 7。我正在访问从主MOC创建的NSManagedObject：

• 当我修改属于主MOC线程）并执行 -save 未触发 -backgroundMOCDidSave：调用


• 当我不修改ManagedObject的任何属性并且只对其MOC执行 -save 操作时触发通知

相同的代码在iOS 6中运行良好。不管是否对ManagedObject进行任何更改，当 -save $ c>

任何人之前遇到过这个问题？ / p>

解决方案

现在我注意到一件事情是错误的，但我不确定它是否导致你的错误。 NSManagedObjectContextDidSaveNotification 在调用 save 的MOC正在运行的线程上发送。但是合并应该在线程MOC合并更改正在运行。在你的情况下，如果更改从背景合并到主要MOC，但没有反过来工作正常。

I have a situation where I make some changes to the properties of a NSManagedObject in main thread. It belongs to the main ManagedObjectContext of the app.

My app does has threading enabled which downloads data, each thread has it's own ManagedObjectContext created from the most recent state of a single PersistentStore throughout the application.

I am implementing NSManagedObjectContextDidSaveNotification so that any changes in the MOC is merged back to the main thread's MOC too. Below is the code for it:

- (void)backgroundMOCDidSave:(NSNotification*)notification
{
    // Probable fix for: http://stackoverflow.com/questions/3446983/collection-was-mutated-while-being-enumerated-on-executefetchrequest
    if (![NSThread isMainThread])
    {
        [self performSelectorOnMainThread:@selector(backgroundMOCDidSave:) withObject:notification waitUntilDone:YES];
        return;
    }

    // We merge the background moc changes in the main moc
    [self.managedObjectContext mergeChangesFromContextDidSaveNotification:notification];
}

Registering for this notification:

        [[NSNotificationCenter defaultCenter] addObserver:self
                                                 selector:@selector(backgroundMOCDidSave:)
                                                     name:NSManagedObjectContextDidSaveNotification
                                                   object:nil];

Strange things happen in iOS 7 though. I am accessing a NSManagedObject which is created from the main MOC:

• When I modify a property of the ManagedObject which belongs to main MOC (main thread) and perform a -save the -backgroundMOCDidSave: call is not triggered
• When I do not modify any property of the ManagedObject and just perform a -save operation on its MOC the notification is triggered

The same code is working perfectly well in iOS 6. Irrespective of whether any changes is done on the ManagedObject or not, when a -save call is triggered on it's MOC the notification NSManagedObjectContextDidSaveNotification gets triggered.

Anyone faced this problem before?

解决方案

For now I've noticed one thing that's wrong, but I'm not sure it's causing your error. NSManagedObjectContextDidSaveNotification is sent on the thread on which MOC that calls save is running. But merging should be made on the thread MOC merging changes is running on. In your case it works fine if changes are merged from the background to the main MOC, but not the other way around.

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