NSFetchedResultsController在从后台线程合并更新后不触发委托方法 [英] NSFetchedResultsController not firing delegate method after merging update from background thread

问题描述

我有一个NSFetchedResultsController和几个操作，通过NSOperationQueue在不同的线程插入和更新托管对象。

I have an NSFetchedResultsController and a few operations that inserts and updates managed objects on separate threads via NSOperationQueue.

FRC看起来像这样， cache to nil：

The FRC looks like this, note that I have set the cache to nil:

[NSFetchedResultsController deleteCacheWithName:nil];
NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:managedObjectContext sectionNameKeyPath:nil cacheName:nil];

每个线程操作都有自己的管理对象上下文，并在每次保存更改时向主MOC调用mergeChangesFromContextDidSaveNotification 。

Each threaded operation has its own managed object context and fires mergeChangesFromContextDidSaveNotification to the main MOC each time it saves changes.

我用来合并上下文的代码如下：

The code that I use to merge contexts looks like this:

- (void)mergeContextChanges:(NSNotification *)notification
{
    NSManagedObjectContext *context = [fetchedResultsController managedObjectContext];

    if([NSThread isMainThread] == NO)
    {
        [self performSelectorOnMainThread:_cmd withObject:notification waitUntilDone:NO];
        return;
    }

    NSSet *updated = [[notification userInfo] objectForKey:NSUpdatedObjectsKey];

    for(NSManagedObject *thing in updated)
    {
        NSLog(@"Background thread updated %@", [thing description]);
    }

    for(NSManagedObject *thing in updated)
    {
        [[context objectWithID:[thing objectID]] willAccessValueForKey:nil];
    }

    [context mergeChangesFromContextDidSaveNotification:notification];
}

我可以通过查看日志来确认每次后台操作插入或更新数据，我的mergeContextChanges：方法正在使用正确的插入/更新值调用。

I can confirm by looking at the logs that each time the background operations insert or update data, my mergeContextChanges: method is being called with the proper insert/update values.

问题是，在合并插入 FRCs委派方法（例如controllerDidChangeContent :)正确，合并更新不会通知FRC触发其委托方法。

The problem is that while merging inserts are firing the FRCs delegate methods (ex. controllerDidChangeContent:) properly, merging updates doesn't signal the FRC to fire its delegate methods.

很奇怪，如果我使用主MOC 在主线程上运行更新，我还可以确认FRC正确地激活其代理。

Strange enough, I can also confirm that the FRC fires its delegates properly if I run the updates on the main thread using the main MOC.

如何在合并更新的MOC时使FRC触发其委托方法？

How can I make the FRC fire its delegate methods when updated MOCs are merged?

更多信息：看起来像使用任何MOC除了主MOC并尝试将更新合并到主MOC具有相同的结果; FRC拒绝注意。

More Info: Looks like using any MOC other than the main MOC and trying to merge updates to the main MOC has the same results; the FRC refuses to notice it.

推荐答案

哦，男人。

看起来像在我的线程操作中访问主MOC（即使它是与我尝试更新的数据无关的任务）导致这种奇怪的行为。

It looks like accessing the main MOC from within my threaded operations (even if it's for a task unrelated to the data I was trying to update) causes this weird behavior.

我希望这可以帮助遇到这个问题的任何人。

I hope this helps anyone else that runs into this problem.

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