ios - 核心数据管理对象上下文保存

Question

我设置了两个 NSManagedObjectContext，一个在主线程上，一个在后台线程上。我目前正在尝试实现 NSFetchedResultsController，但主线程的保存通知似乎不包含像后台线程那样的更改。

关于如何解决这个问题有什么想法吗？这是通知的样子(首先记录后台保存，然后是主保存)。

2014-02-28 15:14:24.210 Lift[62931:70b] Notification found with:
     name:     NSManagingContextDidSaveChangesNotification
     object:   <NSManagedObjectContext: 0x109280700>
     userInfo: {
    inserted = "{(\n)}";
    updated = "{(\n    <Message: 0x109622cc0> (entity: Message; id: 0xd000000000a40006 <x-coredata://B1800ECF-053B-417C-81C0-CD304EF83F19/Message/p41> ; data: {\n    \"awaiting_reply\" = 0;\n    \"body_excerpt\" = \"\\n\\nOn Friday, February 28, 2014 at 12:17 AM, Cody Robertson wrote:\\n\\n> \\n> \\n> On Friday, February 28, 2014 at 12:16 AM, Cody Robertson wrote:\\n> \\n> > \\n> > \\n> > On Friday, February 28, 2014 at 12:12 AM, Co\";\n    cc = \"<relationship fault: 0x109302a10 'cc'>\";\n    date = \"2014-02-28 05:19:19 +0000\";\n    \"expiration_date\" = nil;\n    \"expiration_length\" = 259200;\n    folder = \"lift:in\";\n    from = \"0xd0000000000c0008 <x-coredata://B1800ECF-053B-417C-81C0-CD304EF83F19/UserInfo/p3>\";\n    id = 53101bd032ef5519958b4ecb;\n    mailbox = \"0xd000000000040000 <x-coredata://B1800ECF-053B-417C-81C0-CD304EF83F19/Mailbox/p1>\";\n    read = 0;\n    subject = \"Re: A New Email!\";\n    thread = \"0xd00000000060000a <x-coredata://B1800ECF-053B-417C-81C0-CD304EF83F19/Thread/p24>\";\n    to = \"<relationship fault: 0x1093002a0 'to'>\";\n}),\n    <Message: 0x10975bfd0> (entity: Message; id: 0xd000000000b80006 <x-coredata://B1800ECF-053B-417C-81C0-CD304EF83F19/Message/p46> ; data: {\n    \"awaiting_reply\" = 0;\n    \"body_excerpt\" = \"\\n\";\n    cc = \"<relationship fault: 0x109760580 'cc'>\";\n    date = \"2014-02-28 18:33:25 +0000\";\n    \"expiration_date\" = nil;\n    \"expiration_length\" = 259200;\n    folder = \"lift:in\";\n    from = \"0xd0000000000c0008 <x-coredata://B1800ECF-053B-417C-81C0-CD304EF83F19/UserInfo/p3>\";\n    id = 5310d5eb32ef5519958b4fa7;\n    mailbox = \"0xd000000000040000 <x-coredata://B1800ECF-053B-417C-81C0-CD304EF83F19/Mailbox/p1>\";\n    read = 0;\n    subject = \"New Message\";\n    thread = \"0xd0000000007c000a <x-coredata://B1800ECF-053B-417C-81C0-CD304EF83F19/Thread/p31>\";\n    to = \"<relationship fault: 0x10975e910 'to'>\";\n}),\n   )}";
}
2014-02-28 15:14:24.228 Lift[62931:70b] Notification found with:
     name:     NSManagingContextDidSaveChangesNotification
     object:   <NSManagedObjectContext: 0x10927f670>
     userInfo: {
    inserted = "{(\n)}";
    updated = "{(\n)}";
}

这就是我从后台保存上下文的方式:

- (void)saveFromBackgroundThread:(void(^)(void))completionBlock
{
    NSError *error;
    if (![_backgroundManagedObjectContext save:&error])
    {
        NSLog(@"[BACKGROUND_THREAD] - %@", [error localizedDescription]);
    }

    dispatch_async(dispatch_get_main_queue(), ^{
        NSError *error;
        if (![_mainManagedObjectContext save:&error])
        {
            NSLog(@"[MAIN_THREAD] - %@", [error localizedDescription]);
        }
        else {
            if (completionBlock != nil)
            {
                completionBlock();
            }
        }
    });
}

Answer 1

我应该在 NSManagedObjectContext 类引用文档中找到您的解决方案，特别是阅读“并发”段落。