Ios6 RestKit响应图问题-<；RKMappingResult:，results={"；<；null>=

我正在使用RESTKit0.20.0

{
  "CreateSession" : yes,
  "DistributionChannel" : "string1",
  "Login" : "string2",
  "Nickname" :"string3",
  "Password" :"string4",
  "PhysicalDevice" :
   {
     "DeviceId" : "string5",
     "DeviceTypeCode" : 123,
     "PhysicalDeviceTypeCode" : 1233,
    }
}

是我干的

 NSDictionary * dictionary = @{
                            @"CreateSession":@"yes",
                            @"DistributionChannel":@"string1",
                            @"Login": @"string2",
                            @"Nickname":  @"string3",
                            @"Password":  @"string4",
                            @"PhysicalDevice":  @{ @"DeviceId":  @"string5",
                                                   @"DeviceTypeCode":  @"123",
                                                   @"PhysicalDeviceTypeCode": @"1233" }
                            };


    RKObjectMapping *registerDeviceRequestMapping = [RKObjectMapping requestMapping];
        [registerDeviceRequestMapping addAttributeMappingsFromDictionary:dictionary];

分别为请求和响应创建描述符。将其添加到RKObjectManager共享对象中，还设置了基本url和标头

我打电话来启动这个请求

RKHTTPRequestOperation *operation = [[RKObjectManager sharedManager] appropriateObjectRequestOperationWithObject:dictionary method:RKRequestMethodPOST path:@"RegisterDevice" parameters:nil];

    [operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
         NSLog(@"response   %@",[responseObject description]);

    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
         NSLog(@"Failed with error: %@", [error localizedDescription]);
    }];

        [operation start];

我获得了200个状态，但无法从响应映射值。我得到的映射结果为

<RKMappingResult: 0x849bf60, results={
    "<null>" = "<Response: 0x849b390>";

注意：请求和响应中的值是伪值，但其结构如下所示

{
    "PhysicalDevice": {
        "AddDate": "string1",
        "AuthenticationKey": "string2",
        "DeviceId": "string3",
        "DeviceTypeCode": 33,
        "DeviceTypeName": "string4",
        "Id": 10130,
        "ModDate": "2013-09-27T07:21:34.240Z",
        "PhysicalDeviceTypeCode": 1233,
        "SerialNumber": "string5",
        "Status": 1,
        "StatusName": "string6"
    },
    "RemainingDeviceAssociations": 4,
    "SessionId": "string7"
}