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I am trying to update table view from Core data like this:

    dispatch_queue_t request_queue = dispatch_queue_create("com.myqueue.qu", NULL);
    dispatch_async(request_queue, ^{

        NSManagedObjectContext *parent = [[CoreDataManager instance] managedObjectContext];
        NSManagedObjectContext *searchContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:parent.concurrencyType];
        [searchContext setPersistentStoreCoordinator:[[CoreDataManager instance] persistentStoreCoordinator]];

        NSArray * array = ...// receive array from CoreData, just select, there is no changes

        if (array.count > 0) {

            dispatch_async(dispatch_get_main_queue(), ^{
                block(array);
            });
        }
        else {
            dispatch_async(dispatch_get_main_queue(), ^{
                block(nil);
            });
        }
    });
    dispatch_release(request_queue);

In block I do:

_tableViewData = [array mutableCopy];
[self.tableView reloadData];

But in:

 - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath

My obj:

 MyObj *obj = _tableViewData[indexPath.row];

With nil fields. So obj is empty.

Edit:

I tried to search without creating 'searchContext', using parentContext and tableView updated ok, Is it correct way?

    dispatch_queue_t request_queue = dispatch_queue_create("com.myqueue.qu", NULL);
    dispatch_async(request_queue, ^{

        NSManagedObjectContext *parent = [[CoreDataManager instance] managedObjectContext];

        NSArray * array = ...// receive array from CoreData, using parent as search context

...

4

1 回答 1

1

您不能像这样在线程之间传递托管对象。如果您想在后台线程上运行搜索，您应该将托管对象 ID 传递回表视图，并让它使用 ID 从主线程上下文访问托管对象。当您进行后台提取时，您可以将提取配置为返回 id 而不是完整对象。

于 2013-06-19T07:16:40.057 回答