我一直在查看关于 RestKit 的文档，但我一直无法弄清楚 RKMappingResult 的一些细节。

我有创建 NSManagedObject 的代码，称为 newUser，并插入到 RestKit RKManagedObjectStore 的 mainQueueManagedObjectContext 中。然后，我使用对象管理器的 postObject:path:parameters:success:failure: 方法将用户发布到服务器。这似乎工作正常。

我需要在 post 请求完成时更新 newUser 托管对象上的一些字段，这些字段不会从 post 请求的结果中映射。传递到 block 中的 mappingResult 参数似乎具有与服务器响应中设置的所有字段正确映射的托管对象。

显然，mappingResult 中的对象与我发布的对象不同，因为它们不在同一个线程中。如果我在发布之前保存 newUser，当请求完成并返回映射结果时，它们的 objectID 是否相同？

我在想象 newUser 和映射结果中的对象指的是存储在 CoreData 中的同一个对象，对吗？我问的原因是，情况似乎并非如此。如果我发出一个发布请求并保存 newUser 对象和 mappingResult 中返回的对象，我最终会在 Core Data 中得到两个不同的对象，一个用于 >newUser 和一个用于映射结果。我通过更改 mappingResult 对象和 newUser 对象上的一个字段并看到它们都是独立更改的来确认这一点。此外，在我下次获取时获取两个用户对象。我该如何防止这种情况？

但是，如果这是正确的，那么如果我崩溃了请求还没有完成会怎样？我不会有一个 stub 对象只是卡在 CoreData 中吗？

如果请求失败，如何删除我创建的 stub 对象？我可以在失败 block 中执行类似以下的操作吗？

        dispatch_async(dispatch_get_main_queue(), ^{
            [newUser.managedObjectContext deleteObject:newRegisteredUser];
        });

newUser 是我在 mainQueue 上创建的托管对象。

最后，如果我通过映射结果在后台线程中取回托管对象，我无法将 returnedUser 设置为 UI 用来从中获取信息的用户，因为它在主线程上，所以如何通知用户界面更改它的用户？我应该发布一条通知，告诉 UI 从 Core Data 重新获取事件用户吗？

关于重复对象的更新

我做了一些进一步的测试，当帖子返回时我肯定得到了一个重复的对象。

我首先创建一个 newUser 并为其设置属性:

HNGRRegisteredUser *newUser = [NSEntityDescription insertNewObjectForEntityForName:@"RegisteredUser" inManagedObjectContext:context];
newUser.firstName = @"John"
newUser.lastName = @"Smith"
newUser.gender = @"Male"
newUser.email = @"js@email.com"
newUser.hungrosityModel = //fill in all of the attributes for a hungrosityModel, except uniqueID

此时，newUser.uniqueID == nil。然后我保存 newUser(我假设我必须这样做，以便 RestKit 可以使用永久 objectID)，以创建一个 stub 对象。

NSError *saveError;
[newRegisteredUser.managedObjectContext saveToPersistentStore:&saveError];
if (saveError) NSLog(@"Save Error: %@", saveError);
NSLog(@"newUser objectID: %@", [newRegisteredUser.objectID URIRepresentation]);

然后我发布 newUser 对象。

[[RKObjectManager sharedManager] postObject:newRegisteredUser path:@"users/" parameters:nil success:^(RKObjectRequestOperation *operation, RKMappingResult *mappingResult) {
    NSError *saveError;
    HNGRRegisteredUser *returnedUser = [mappingResult firstObject];
    NSLog(@"mappingResult objectID: %@", [returnedUser.objectID URIRepresentation]);

    [returnedUser.managedObjectContext saveToPersistentStore:&saveError];
    if (saveError) NSLog(@"Error saving user upon registration: %@", saveError);
} failure:^(RKObjectRequestOperation *operation, NSError *error) {
    [newUser.managedObjectContext deleteObject:newUser];
}];

objectID 的打印输出如下。

newUser objectID: x-coredata://B74AB613-1060-4D98-ABFC-3B4D89AB12C3/RegisteredUser/p2
mappingResult objectID: x-coredata://B74AB613-1060-4D98-ABFC-3B4D89AB12C3/RegisteredUser/p3

发送到服务器的 JSON 是:

{
    "gender":"Male",
    "lastName":"Smith",
    "firstName":"John",
    "email":"js@email.com",
    "hungrosityModel": {
        "totalNumberOfUpdates":0,
        "peakHungrosity":0.8,
        "hungrosityFractionAtLastUpdate":0,
        "rateOfHungrosification":5e-05,
        "troughHungrosity":0.1,
        "peakUpdates":0
    }
}

从服务器返回的 JSON 是:

{"results": [
    {"receivedFriendRequests": [],
     "firstName": "John",
     "middleName": null,
     "hungrosityModel": {"uniqueID": 13},
     "email": "js@email.com",
     "gender": "Male",
     "lastName": "Smith",
     "sentFriendRequests": [],
     "uniqueID": 14,
     "updatedAt": "2014-03-12T17:45:01.973Z",
     "friends": [],
     "profileImageUpdatedAt": null,
     "createdAt": "2014-03-12T17:45:01.809Z"}
 ]}

对象的响应和请求描述符是:

[[RKObjectManager sharedManager].router.routeSet addRoute:[RKRoute routeWithClass:[HNGRRegisteredUser class] pathPattern:@"users/" method:RKRequestMethodPOST]];

RKResponseDescriptor *registrationResponseDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:[HNGRRKMappingProvider registeredUserMapping] method:RKRequestMethodPOST pathPattern:@"users/" keyPath:@"results" statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)];
[[RKObjectManager sharedManager] addResponseDescriptor: registrationResponseDescriptor];

RKRequestDescriptor *registrationRequestDescriptor = [RKRequestDescriptor requestDescriptorWithMapping:[[HNGRRKMappingProvider registeredUserMapping] inverseMapping] objectClass:[HNGRRegisteredUser class] rootKeyPath:nil method:RKRequestMethodPOST];
[[RKObjectManager sharedManager] addRequestDescriptor:registrationRequestDescriptor];

用户的映射是:

RKEntityMapping *_mapping = nil;
_mapping = [RKEntityMapping mappingForEntityForName:@"RegisteredUser" inManagedObjectStore:[RKManagedObjectStore defaultStore]];
[_mapping addAttributeMappingsFromArray:@[@"uniqueID",
                                           @"createdAt",
                                           @"updatedAt",
                                           @"firstName",
                                           @"middleName",
                                           @"lastName",
                                           @"email",
                                           @"gender",
                                           @"profileImageUpdatedAt"]];
[_mapping addRelationshipMappingWithSourceKeyPath:@"hungrosityModel" mapping:[HNGRRKMappingProvider basicModelMapping]];
_mapping.identificationAttributes = @[@"uniqueID"];

这里是相关的对象映射轨迹:

D restkit.object_mapping:RKMapperOperation.m:377 Executing mapping operation for representation: {
        results =     (
                    {
                createdAt = "2014-03-12T18:22:35.688Z";
                dateOfBirth = "2014-03-12T18:24:02Z";
                firstName = John;
                friends =             (
                );
                gender = Male;
                hungrosityModel =             {
                    uniqueID = 14;
                };
                lastName = Smith;
                middleName = "<null>";
                profileImageUpdatedAt = "<null>";
                receivedFriendRequests =             (
                );
                sentFriendRequests =             (
                );
                uniqueID = 14;
                updatedAt = "2014-03-12T18:22:35.856Z";
            }
        );
    }
     and targetObject: <HNGRRegisteredUser: 0xaa8c180> (entity: RegisteredUser; id: 0xa894550 <x-coredata://44B8DF7A-BDC9-45F2-A137-BFAACF4AAF88/RegisteredUser/p2> ; data: {
        createdAt = nil;
        dateOfBirth = "2014-03-12 18:24:02 +0000";
        email = "js@email.com";
        firstName = John;
        friendRequests = "<relationship fault: 0xa899dd0 'friendRequests'>";
        friends = "<relationship fault: 0xa891ea0 'friends'>";
        gender = Male;
        hungrosityModel = "0xa861980 <x-coredata://44B8DF7A-BDC9-45F2-A137-BFAACF4AAF88/BasicModel/p2>";
        hungrosityUpdateEvents = "<relationship fault: 0xa829d90 'hungrosityUpdateEvents'>";
        isLocalUser = 0;
        lastName = Smith;
        middleName = nil;
        myInvitations = nil;
        profileImageData = nil;
        profileImageThumbnailData = nil;
        profileImageUpdatedAt = nil;
        receivedInvitations = nil;
        registeredUserSettings = nil;
        savedHungrosityComments = "<relationship fault: 0xa8bc450 'savedHungrosityComments'>";
        uniqueID = nil;
        updatedAt = nil;
        user = nil;
        userSettings = nil;
    })
  T restkit.object_mapping:RKMapperOperation.m:320 Examining keyPath 'results' for mappable content...
  D restkit.object_mapping:RKMapperOperation.m:297 Found mappable collection at keyPath 'results': (
            {
            createdAt = "2014-03-12T18:22:35.688Z";
            dateOfBirth = "2014-03-12T18:24:02Z";
            firstName = John;
            friends =         (
            );
            gender = Male;
            hungrosityModel =         {
                uniqueID = 14;
            };
            lastName = Smith;
            middleName = "<null>";
            profileImageUpdatedAt = "<null>";
            receivedFriendRequests =         (
            );
            sentFriendRequests =         (
            );
            uniqueID = 14;
            updatedAt = "2014-03-12T18:22:35.856Z";
        }
    )

 D restkit.object_mapping:RKMappingOperation.m:952 Starting mapping operation...
 T restkit.object_mapping:RKMappingOperation.m:953 Performing mapping operation: <RKMappingOperation 0xa8e4440> for 'HNGRRegisteredUser' object. Mapping values from object {
    createdAt = "2014-03-12T18:22:35.688Z";
    dateOfBirth = "2014-03-12T18:24:02Z";
    firstName = John;
    friends =     (
    );
    gender = Male;
    hungrosityModel =     {
        uniqueID = 14;
    };
    lastName = Smith;
    middleName = "<null>";
    profileImageUpdatedAt = "<null>";
    receivedFriendRequests =     (
    );
    sentFriendRequests =     (
    );
    uniqueID = 14;
    updatedAt = "2014-03-12T18:22:35.856Z";
} to object <HNGRRegisteredUser: 0xa8833b0> (entity: RegisteredUser; id: 0xa8777e0 <x-coredata:///RegisteredUser/t1FD3D8DE-75AD-4194-B157-EB6931B74BDB6> ; data: {
    createdAt = nil;
    dateOfBirth = nil;
    email = nil;
    firstName = nil;
    friendRequests =     (
    );
    friends =     (
    );
    gender = nil;
    hungrosityModel = nil;
    hungrosityUpdateEvents =     (
    );
    isLocalUser = 0;
    lastName = nil;
    middleName = nil;
    myInvitations = nil;
    profileImageData = nil;
    profileImageThumbnailData = nil;
    profileImageUpdatedAt = nil;
    receivedInvitations = nil;
    registeredUserSettings = nil;
    savedHungrosityComments =     (
    );
    uniqueID = 14;
    updatedAt = nil;
    user = nil;
    userSettings = nil;
}) with object mapping (null)

如果有更多信息有助于了解，请告诉我。

最佳答案

是的，对象 ID 将始终匹配(即使托管对象实例不同，它仍然表示相同的底层实体实例)。它们通常是您在主线程上启动时相同的托管对象实例，RestKit 也会在主线程上调用您。

您描述的新实例不会发生。您发布的原始对象应该直接更新。在您的情况下，这不会发生，因为服务器正在返回一个对象数组。这导致 RestKit 忽略提供的目标对象并创建新的目标对象。在本例中，这是一个新对象，因为数组包含一项。要解决此问题，您需要修改来自服务器的 JSON，因为您无法将数组作为映射的一部分进行索引...

要删除，您不需要切换线程(但如果您希望将来进行验证，您可以切换线程)，这是正确的方法。

您可以发布通知。我通常使用 fetched results controller，因为它会为您管理观察变化。

关于ios - RestKit postObject 方法中的 post 对象和它返回的 RKMappingResult 是什么关系？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/22343101/