Question

我有一些代码可以将课程作为JSON下载，解析它们并将它们放入核心数据中。然后它们显示在UITableView中。目前，当用户有许多课程时，连接有时会超时。所以我试图解析课程（使用SBJson）并一次将它们添加到tableview中。

两者的代码基本相同，但是当tableView内容出现时，新代码导致崩溃，错误

"Terminating app due to uncaught exception 
'NSObjectInaccessibleException', reason: 'The NSManagedObject with ID:0x5ad0570 <x-coredata://A21AC71F-175B-423D-BF7D-C67BEE094460/Lessons/p18> has been invalidated.'"

我想知道可能导致此错误的这两个代码清单之间的区别。原始代码在循环中创建每个核心数据对象，但新代码在下载时创建每个核心数据对象。 listViewArray是用于填充UITableView的数组。

我正在使用SBJsonStreamParser和SBJsonStreamParserAdapter来解析Json。

我确实有一个工作实现（未显示），每次收到一个新对象时基本上调用下面的原始代码（每次都通过完整的接收对象循环）。我想知道导致错误的原因，不仅仅是让事情有效。

这是原始的非流式代码，在connectionDidFinishLoading中调用：

    NSMutableArray *tempListArray = [[NSMutableArray alloc] initWithArray:jsonStreamedData];

    if (listViewArray)
        [listViewArray release];
    listViewArray = [[NSMutableArray alloc] init];

    if(![tempListArray count]){
        UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Message" message:@"No active lessons " delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];
        [alertView show];
        [alertView release];
    }
    else {
        MyAppDelegate *appDelegate = (MyAppDelegate *)[[UIApplication sharedApplication] delegate];
        NSError *error = nil;
        [appDelegate.managedObjectContext reset];

        NSManagedObjectContext *managedObjectContext = appDelegate.managedObjectContext;
        for (int i = 0; i < [tempListArray count]; i++) {

            NSFetchRequest *checkRequest = [[NSFetchRequest alloc] init];
            NSEntityDescription *lessonEntity = [NSEntityDescription entityForName:@"Lessons" inManagedObjectContext:managedObjectContext];
            [checkRequest setEntity:lessonEntity];
            NSPredicate *langPredicate = [NSPredicate predicateWithFormat:@"(language = %@)", appDelegate.currentLanguage];
            NSPredicate *userPredicate = [NSPredicate predicateWithFormat:@"(username = %@)", appDelegate.userName];
            NSPredicate *idPredicate = [NSPredicate predicateWithFormat:@"(content_Id = %@)", [[tempListArray objectAtIndex:i] valueForKey:@"id"]];
            [checkRequest setPredicate:[NSCompoundPredicate andPredicateWithSubpredicates:[NSArray arrayWithObjects:langPredicate, userPredicate, idPredicate, nil]]];

            NSArray *checkResults = [managedObjectContext executeFetchRequest:checkRequest error:&error];
            [checkRequest release];

            NSMutableDictionary *tempDict = [[NSMutableDictionary alloc] init];
            if ([checkResults count]) {
                Lessons *lessonObj = [checkResults objectAtIndex:0];
                lessonObj.cards_count = [[tempListArray objectAtIndex:i] valueForKey:@"cards_count"];
                lessonObj.mTitle = [[tempListArray objectAtIndex:i] valueForKey:@"title"];
                lessonObj.sound_Url = [[tempListArray objectAtIndex:i] valueForKey:@"audio_url"];
                lessonObj.mId = [NSNumber numberWithInt:i];
                [tempDict setValue:lessonObj forKey:@"lesson"];
                [tempDict setValue: [[tempListArray objectAtIndex:i]  objectForKey:@"image_url"] forKey:@"image_url"];
                [listViewArray addObject:tempDict];

            }
            else {

                Lessons *newLesson = (Lessons *)[NSEntityDescription insertNewObjectForEntityForName:@"Lessons" inManagedObjectContext:appDelegate.managedObjectContext];
                newLesson.cards_count = [[tempListArray objectAtIndex:i] valueForKey:@"cards_count"];
                newLesson.mTitle = [[tempListArray objectAtIndex:i] valueForKey:@"title"];
                newLesson.sound_Url = [[tempListArray objectAtIndex:i] valueForKey:@"audio_url"];
                newLesson.content_Id = [[tempListArray objectAtIndex:i] valueForKey:@"id"];
                newLesson.username = appDelegate.userName;
                newLesson.language = appDelegate.currentLanguage;
                newLesson.mId = [NSNumber numberWithInt:i];
                [tempDict setValue:newLesson forKey:@"lesson"];
                [tempDict setValue: [[tempListArray objectAtIndex:i]  objectForKey:@"image_url"] forKey:@"image_url"]; 
                [listViewArray addObject:tempDict];

            }
            [tempDict release];
            tempDict = nil;
        }


        if (![appDelegate.managedObjectContext save:&error]) {
            NSLog(@"Core Data Error - %@", [error localizedDescription]);

        }   

        //      NSMutableArray *tempArray = [NSMutableArray arrayWithArray:listViewArray];
        //      [listViewArray removeAllObjects];
        //      [listViewArray addObjectsFromArray:[[tempArray reverseObjectEnumerator] allObjects]];
        //      tempArray = nil;
    }
    [tempListArray release];
}
[mListsTableView reloadData];

以下是崩溃的代码，在解析器中调用：foundObject：循环代码已被删除，因为每次下载新的Json对象时都会调用它。

    [jsonStreamedData addObject:dict];
    if (!listViewArray)
        listViewArray = [[NSMutableArray alloc] init];

    MyAppDelegate *appDelegate = (MyAppDelegate *)[[UIApplication sharedApplication] delegate];
    NSError *error = nil;
    [appDelegate.managedObjectContext reset];

    NSManagedObjectContext *managedObjectContext = appDelegate.managedObjectContext;

    NSFetchRequest *checkRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *lessonEntity = [NSEntityDescription entityForName:@"Lessons" inManagedObjectContext:managedObjectContext];
    [checkRequest setEntity:lessonEntity];
    NSPredicate *langPredicate = [NSPredicate predicateWithFormat:@"(language = %@)", appDelegate.currentLanguage];
    NSPredicate *userPredicate = [NSPredicate predicateWithFormat:@"(username = %@)", appDelegate.userName];
    NSPredicate *idPredicate = [NSPredicate predicateWithFormat:@"(content_Id = %@)", [dict valueForKey:@"id"]];
    [checkRequest setPredicate:[NSCompoundPredicate andPredicateWithSubpredicates:[NSArray arrayWithObjects:langPredicate, userPredicate, idPredicate, nil]]];

    NSArray *checkResults = [managedObjectContext executeFetchRequest:checkRequest error:&error];
    [checkRequest release];

    NSMutableDictionary *tempDict = [[NSMutableDictionary alloc] init];

    if ([checkResults count]) {
        Lessons *lessonObj = [checkResults objectAtIndex:0];
        lessonObj.cards_count = [dict valueForKey:@"cards_count"];
        lessonObj.mTitle = [dict  valueForKey:@"title"];
        lessonObj.sound_Url = [dict valueForKey:@"audio_url"];
        lessonObj.mId = [NSNumber numberWithInt:jsonStreamedData.count - 1]; // This should be equivalent to i from the loop in the first code
        [tempDict setValue:lessonObj forKey:@"lesson"];
        [tempDict setValue: [dict objectForKey:@"image_url"] forKey:@"image_url"];
        [listViewArray addObject:tempDict];

    }
    else {

        Lessons *newLesson = (Lessons *)[NSEntityDescription insertNewObjectForEntityForName:@"Lessons" inManagedObjectContext:appDelegate.managedObjectContext];
        newLesson.cards_count = [dict valueForKey:@"cards_count"];
        newLesson.mTitle = [dict valueForKey:@"title"];
        newLesson.sound_Url = [dict valueForKey:@"audio_url"];
        newLesson.content_Id = [dict valueForKey:@"id"];
        newLesson.username = appDelegate.userName;
        newLesson.language = appDelegate.currentLanguage;
        newLesson.mId = [NSNumber numberWithInt:jsonStreamedData.count - 1];
        [tempDict setValue:newLesson forKey:@"lesson"];
        [tempDict setValue: [dict  objectForKey:@"image_url"] forKey:@"image_url"]; 
        [listViewArray addObject:tempDict];

    }

    [tempDict release];
    tempDict = nil;

    if (![appDelegate.managedObjectContext save:&error]) {
        ALog(@"Core Data Error - %@", [error localizedDescription]);
    }   

    //  NSMutableArray *tempArray = [NSMutableArray arrayWithArray:listViewArray];
    //  [listViewArray removeAllObjects];
    //  [listViewArray addObjectsFromArray:[[tempArray reverseObjectEnumerator] allObjects]];
    //  tempArray = nil;
//[self getListsLocally];
[mListsTableView reloadData];

最后，这是在使用第二个列表时崩溃的实际部分，在tableView中：cellForRowAtIndexPath：顺便说一句，它在行== 1时崩溃，而不是行== 0.由于某种原因，第0行没问题。当然，它永远不会有机会加载其他行。

        titleLabel.text = [[[listViewArray objectAtIndex:indexPath.row] valueForKey:@"lesson"] valueForKey:@"mTitle"]; // CRASH!
        labelCards.text = [NSString stringWithFormat:@"%@ Cards", [[[listViewArray objectAtIndex:indexPath.row]  valueForKey:@"lesson"] valueForKey:@"cards_count"]];

        if([[listViewArray objectAtIndex:indexPath.row] objectForKey:@"userImageObj"] == nil){
            mImageView.backgroundColor = [UIColor grayColor];
            if ([[listViewArray objectAtIndex:indexPath.row] objectForKey:@"isThreadLaunched"] == nil) {
                [NSThread detachNewThreadSelector:@selector(loadImagesInBackground:) toTarget:self withObject:[NSNumber numberWithInt:indexPath.row]];
                [[listViewArray objectAtIndex:indexPath.row] setObject:@"Yes" forKey:@"isThreadLaunched"];
            }
        }else {
            mImageView.image = [[listViewArray objectAtIndex:indexPath.row] objectForKey:@"userImageObj"];
        }

Answer 1

当您在运行fetch之前立即在managedObjectContext上调用reset时，很可能会发生对象失效。调用reset会使内存中的对象无效，但在保存之前不会删除它们。如果另一个对象（如数组）保留了无效的托管对象，则它将保持在无效表单中的保存之后。当您运行fetch时，fetch会返回失效的对象，当您尝试访问其中一个属性时会导致错误

当与撤消管理器一起使用时，将调用

reset。它不是通用的“擦除上下文”调用。如果要删除现有对象，则需要获取它们并明确删除它们。

您的代码还有其他一些问题。即使您没有创建它，也可以在release阵列上调用checkRequest。这可能导致阵列随机消失。同样，listViewArray似乎是一个类属性，但您从不使用访问者表单，例如self.listViewArray以确保妥善保留。

Answer 2

最可能的原因是解析器没有在主线程上运行，并且你在主线程和解析器中使用相同的ManagedObjectContext - 你不能这样做 - 保证会引起各种奇怪的行为。

您需要在解析器中创建一个新的ManagedObjectContext，并将其与主线程的ManagedObjectContext的persistentStore相关联

CoreData框架非常清楚 - 你不能跨线程边界共享ManagedObjectContext

Core-Data NSObjectInaccessibleException NSManagedObject已失效

2 个答案: