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这是我的代码：

        LoadViewController *loadingViewController = [[LoadViewController alloc] initWithNibName:@"LoadViewController" bundle:nil];
[self.view addSubview:loadingViewController.view];

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0) , ^{
    [Util deleteAllObjects:@"Unit"];
    for (NSDictionary *eachUnit in serviceData) {
        //insert in DB
        AppDelegate* appDelegate = [AppDelegate sharedAppDelegate];
        NSManagedObjectContext *context = appDelegate.managedObjectContext;
        Unit *unit = [NSEntityDescription insertNewObjectForEntityForName:@"Unit" inManagedObjectContext:context];

        unit.id_unidade = [eachUnit objectForKey:@"id"];
        unit.title = [eachUnit objectForKey:@"title"];
        unit.image = [eachUnit objectForKey:@"image"];
        unit.address = [eachUnit objectForKey:@"address"];
        unit.desc = [eachUnit objectForKey:@"desc"];
        unit.coord = [eachUnit objectForKey:@"coord"];

        NSError *error;

        if (![context save:&error]) {
            NSLog(@"Ops,fail: %@", [error localizedDescription]);
        }
    }
    NSLog(@"before");
    [self fillUnits];
    NSLog(@"after");

    dispatch_async(dispatch_get_main_queue(), ^(void) {
        NSLog(@"reload");
        [self.tableView reloadData];
        [loadingViewController.view removeFromSuperview];
        NSLog(@"after reload");

    });
});

它一直显示到 NSLog(@"after")，但永远不会出现在 NSLog(@"reload") 上。有什么线索吗？？

4

1 回答 1

1

在您的完成处理程序中，您需要确保所有发送到托管对象或托管对象上下文的方法都使用或在它们各自的执行上下文中执行：performBlock:performBlockAndWait:

    NSManagedObjectContext *context = appDelegate.managedObjectContext;
    [context performBlockAndWait:^{
        Unit *unit = [NSEntityDescription insertNewObjectForEntityForName:@"Unit"  inManagedObjectContext:context];

        unit.id_unidade = [eachUnit objectForKey:@"id"];
        unit.title = [eachUnit objectForKey:@"title"];
        unit.image = [eachUnit objectForKey:@"image"];
        unit.address = [eachUnit objectForKey:@"address"];
        unit.desc = [eachUnit objectForKey:@"desc"];
        unit.coord = [eachUnit objectForKey:@"coord"];

        NSError *error;
        if (![context save:&error]) {
            NSLog(@"Ops,fail: %@", [error localizedDescription]);
        }
    }];

如果将在主线程中访问您的托管对象，则执行上下文必须等于主线程。

您可以在 Apple Docs 中阅读更多内容：NSManagedObjectContext Reference，尤其是“并发”一章。

于 2014-01-08T14:34:08.620 回答