RestKit：'NSInternalInconsistencyException'，原因：'无法执行映射：没有分配`managedObjectContext`

Question

我收到以下错误：

*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Unable to perform mapping: No `managedObjectContext` assigned. (Mapping response.URL = https://www.someurl.com/lastrequest=2014-12-08T02%3A44%3A52Z)'

应用程序在 RKResponseMapperOperation.m 中的以下行停止：

- (RKMappingResult *)performMappingWithObject:(id)sourceObject error:(NSError **)error
{

    NSLog(@"managedObjectContext: %@,    Source Object: %@        Error: %@", self.managedObjectContext, sourceObject, (*error).description);
    NSAssert(self.managedObjectContext, @"Unable to perform mapping: No `managedObjectContext` assigned. (Mapping response.URL = %@)", self.response.URL);
....

我注意到在应用程序崩溃之前，上述方法被调用了 27 次（这个数字不同）。在每个实例中，都存在 NSManagedObjectContext，即下面的行：

2014-12-07 18:44:48.721 MyApp[19011:3258405] managedObjectContext:managedObjectContext: <NSManagedObjectContext: 0x1701f5800>,    Source Object: {
    friends =     (
    );
}        Error: (null)

然而就在它崩溃之前，NSManagedObjectContext 为空：

2014-12-07 18:44:53.454 MyApp[19011:3258404] managedObjectContext: (null),    Source Object: {
    friends =     (
    );
}        Error: (null)

由于应用程序在崩溃之前可以正常运行一段时间，我不知道如何解决这个问题。任何指针将不胜感激。

* 编辑 *

在 Appdelegate 中。该方法在用户登录时在 viewDidLoad 中调用一次。

- (RKManagedObjectStore *)managedObjectStore
{
    if (!_managedObjectStore && [Persistence loggedIn])
    {
        NSError * error;
        NSURL * modelURL = [NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"App" ofType:@"momd"]];
        NSManagedObjectModel * managedObjectModel = [[[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL] mutableCopy];
        self.managedObjectStore = [[RKManagedObjectStore alloc] initWithManagedObjectModel:managedObjectModel];

        [_managedObjectStore createPersistentStoreCoordinator];

        NSArray * searchPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
        NSString * documentPath = [searchPaths objectAtIndex:0];

        NSString *dbName = [NSString stringWithFormat:@"%@App%@.sqlite", documentPath, [Persistence username]];
        NSPersistentStore * persistentStore = [_managedObjectStore addSQLitePersistentStoreAtPath:dbName
                                                                           fromSeedDatabaseAtPath:nil
                                                                                withConfiguration:nil
                                                                                          options:[self optionsForSqliteStore]
                                                                                            error:&error];
        NSAssert(persistentStore, @"Failed to add persistent store with error: %@", error);

        NSLog(@"Path: %@", dbName);

        if(!persistentStore)
        {
            NSLog(@"Failed to add persistent store: %@", error);
        }

        [_managedObjectStore createManagedObjectContexts];
        self.managedObjectStore.managedObjectCache = [[RKInMemoryManagedObjectCache alloc] initWithManagedObjectContext:self.managedObjectStore.persistentStoreManagedObjectContext];

        return self.managedObjectStore;
    }

    return _managedObjectStore;
}

- (id)optionsForSqliteStore
{
    return @{
             NSInferMappingModelAutomaticallyOption: @YES,
             NSMigratePersistentStoresAutomaticallyOption: @YES
             };
}

创建 MOC： 对于 Core Data 堆栈，我使用的是在 Xcode 中创建项目时提供的 AppDelegate 中的 Default Core Data 代码。

- (NSManagedObjectContext *)managedObjectContext
{
    if (_managedObjectContext != nil) {
        return _managedObjectContext;
    }

    NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
    if (coordinator != nil) {
        _managedObjectContext = [[NSManagedObjectContext alloc] init];
        [_managedObjectContext setPersistentStoreCoordinator:coordinator];
    }
    return _managedObjectContext;
}

MOC操作：

- (void)saveContext
{
    NSError *error = nil;
    NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
    if (managedObjectContext != nil) {
        if ([managedObjectContext hasChanges] && ![managedObjectContext save:&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();
        } 
    }
}

在App内部，以下方法用于设置、获取和清除ObjectManager：

- (void)refreshMOC
{
    AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
    self.objectManager = [self getObjectManager];

    self.objectManager.managedObjectStore = appDelegate.managedObjectStore;
    self.objectManager.managedObjectStore.managedObjectCache = appDelegate.managedObjectStore.managedObjectCache;
    self.managedObjectContext = self.objectManager.managedObjectStore.mainQueueManagedObjectContext;
}

- (RKObjectManager *)setupObjectManager
{
    NSURL *baseURL = [NSURL URLWithString:kBaseURL];
    AFHTTPClient *httpClient = [[AFHTTPClient alloc]initWithBaseURL:baseURL];
    RKObjectManager *manager = [[RKObjectManager alloc]initWithHTTPClient:httpClient];
    [manager.HTTPClient registerHTTPOperationClass:[AFJSONRequestOperation class]];
    [manager setAcceptHeaderWithMIMEType:RKMIMETypeJSON];
    [manager.HTTPClient setParameterEncoding:AFJSONParameterEncoding];
    [RKMIMETypeSerialization registeredMIMETypes];
    [RKObjectManager setSharedManager:manager];

    return [RKObjectManager sharedManager];
}

- (RKObjectManager *)getObjectManager
{
    self.objectManager = (!self.objectManager) ?  [self setupObjectManager] : self.objectManager;
    return self.objectManager;
}

- (RKObjectManager*)newObjectManager
{
    [self clearRKObjectManager];
    return [self getObjectManager];
}

- (void)clearRKObjectManager
{
    if (self.objectManager)
    {
        self.objectManager = nil;
    }
}

Answer 1

删除所有应用程序委托模板 Core Data 方法。当您使用 RestKit 并创建托管对象存储时，您要求 RestKit 为您管理核心数据堆栈，因此不需要那些其他方法（并且会混淆事情）。

当您需要 MOC 时，从托管对象存储中获取它/一个。

注意，以上内容也适用于保存，因为您需要使用 RestKit 方法保存到持久存储，而不是仅保存单个 MOC。