ios - 在 Restkit 0.2 中加载具有相同实体和不同谓词的两个不同表时遇到问题

Question

这是我正在尝试做的简化版本:

我有一个使用 UITabBarController 作为根 Controller 的应用程序。在两个选项卡中，我有一个包含自定义 UITableViewController 的 UINavigationController。

其中一个 Tableview 用于显示“特色”项目，另一个用于显示“用户”项目。

第一个的 API 端点是:/api/items/featured另一个端点是:/api/items/user

我经历了在 AppDelegate.m 中设置所有内容的整个过程:

// Configure the object manager
RKObjectManager *objectManager = [RKObjectManager managerWithBaseURL:[NSURL URLWithString:API_SERVER]];
objectManager.managedObjectStore = managedObjectStore;
[RKObjectManager setSharedManager:objectManager];

RKEntityMapping *entityMapping = [RKEntityMapping mappingForEntityForName:@"Item" inManagedObjectStore:managedObjectStore];
[entityMapping addAttributeMappingsFromDictionary:@{
 @"id":                     @"itemID",
 @"type":                   @"type",
 @"created_at":             @"created_at":
 @"field1":                 @"field1"}];

// User Descriptor
RKResponseDescriptor *userDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:entityMapping pathPattern:@"/api/items/user" keyPath:nil statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)];

[objectManager addResponseDescriptor:userDescriptor];

// Featured Listing Decriptor
RKResponseDescriptor *featuredDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:entityMapping pathPattern:@"/api/items/featured" keyPath:nil statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)];

[objectManager addResponseDescriptor:responseDescriptor];

然后在 TableViewControls 中我有以下内容(在第二个 tableview Controller 中用“user”替换“featured”)

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    [self loadItems];
}

- (void)loadItems {    
    [[RKObjectManager sharedManager] getObjectsAtPath:@"/api/items/featured" parameters:nil 
        success:^(RKObjectRequestOperation *operation, RKMappingResult *mappingResult) {
    self.lastupdate = [[NSDate alloc] init];
    } 
        failure:^(RKObjectRequestOperation *operation, NSError *error) {
    UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"An Error Has Occurred" message:[error localizedDescription] delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
    [alertView show];
    }];
}

- (NSFetchedResultsController *)fetchedResultsController {
    if (_fetchedResultsController != nil) {
        return _fetchedResultsController;
    }
    RKManagedObjectStore *managedObjectStore = [RKManagedObjectStore defaultStore];
    self.managedObjectContext = managedObjectStore.mainQueueManagedObjectContext;

    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    // Edit the entity name as appropriate.
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Item" inManagedObjectContext:self.managedObjectContext];

    [fetchRequest setEntity:entity];

    // Set the batch size to a suitable number.
    [fetchRequest setFetchBatchSize:20];

    // Edit the sort key as appropriate.
    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"created_at" ascending:NO];
    NSArray *sortDescriptors = @[sortDescriptor];

    [fetchRequest setSortDescriptors:sortDescriptors];

    // Set predicate to only get Featured Listings
    NSPredicate *predicate = [NSPredicate predicateWithFormat: @"type like 'featured'"];
    [fetchRequest setPredicate:predicate];

    // Edit the section name key path and cache name if appropriate.
    // nil for section name key path means "no sections".
    NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:@"Master"];
    aFetchedResultsController.delegate = self;
    self.fetchedResultsController = aFetchedResultsController;

    NSError *error = nil;

    if (![self.fetchedResultsController performFetch:&error]) {
        // Replace this implementation with code to handle the error appropriately.
        // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }

    return _fetchedResultsController;
}

现在第一个选项卡一切正常(目前它返回 8 个项目，type = 'featured'，显示在表格中)。

当我切换到第二个选项卡时，问题就来了。它目前只返回 1 个类型为“用户”的项目，并且崩溃:

CoreData: error: Serious application error. Exception was caught during Core Data change processing. This is usually a bug within an observer of NSManagedObjectContextObjectsDidChangeNotification. * -[__NSArrayM objectAtIndex:]: index 3 beyond bounds for empty array with userInfo (null)

如果我在“用户”选项卡上省略谓词，则“特色”选项卡可以正常工作，“用户”选项卡会在其表中获取“特色”项目，“用户”项目位于顶部。

由于这两个 tableview 控件的代码是相同的，除了“user”和“featured”，我不知道问题出在哪里。

Answer 1

当您创建和配置您的抓取结果 Controller 时，不要使用缓存。目前他们都在使用 @"Master" 的缓存，这将导致他们尝试共享不合适的信息，因为获取请求不同。