ios - 使用 RestKIt 在核心数据实体中映射 json 对象

Question

我正在使用 RestKit 开发一些待办事项列表应用程序。我面临一些关于在 iOS 中使用 CoreData 返回的 json 表单服务器的映射问题。

场景

以下是我正在使用的列表和任务实体的图像。

当有人将新任务添加到服务器上的列表时，我返回该特定列表的 Json:

`GET www.mydomain.com\api\list\1`

        [ { "list" : 

          { "listID" : "1",
            "listName" : "New List ",
            "listSyncStatus" : "1"
          },
        "tasks" : [ { "listID" : "1",
              "taskCompletionStatus" : "1",
              "taskID" : "24",
              "taskName" : "Server Added 2",
              "taskSyncStatus" : "1"
            },
            { "listID" : "1",
              "taskCompletionStatus" : "1",
              "taskID" : "25",
              "taskName" : "Server Added 3",
              "taskSyncStatus" : "1"
            },
            { "listID" : "1",
              "taskCompletionStatus" : "1",
              "taskID" : "23",
              "taskName" : "Server Added",
              "taskSyncStatus" : "1"
            }
          ]
      } 
    ]

我对上述 json 的响应描述符如下:

    RKResponseDescriptor *taskResponseDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:taskEntityMapping
                                                                                            method:RKRequestMethodGET
                                                                                       pathPattern:@"/api/list/:id"
                                                                                           keyPath:@"tasks"
                                                                                       statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)];

对于我的核心数据映射，我使用以下关系映射:

    [taskEntityMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"list"
                                                                                  toKeyPath:@"list"
                                                                                withMapping:listEntityMapping]];

我的taskEntityMapping如下:

    NSDictionary *taskObjectMapping = @{
                                    @"listID" : @"listID",
                                    @"taskID" : @"taskID",
                                    @"taskName" : @"taskName",
                                    @"taskCompletionStatus" : @"taskCompletionStatus",
                                    @"taskSyncStatus" : @"taskSyncStatus"
                                };

RKEntityMapping *taskEntityMapping = [RKEntityMapping mappingForEntityForName:@"Task" inManagedObjectStore:managedObjectStore];
[taskEntityMapping addAttributeMappingsFromDictionary:taskObjectMapping];
taskEntityMapping.identificationAttributes = @[ @"taskID" ];

和我的listEntityMapping如下:

    //ALL LISTS RELATED REQUESTS
NSDictionary *listObjectMapping = @{
                                      @"listID" : @"listID",
                                      @"listName" : @"listName",
                                      @"listSyncStatus" : @"listSyncStatus",

                                  };

RKEntityMapping *listEntityMapping = [RKEntityMapping mappingForEntityForName:@"List" inManagedObjectStore:managedObjectStore];
[listEntityMapping addAttributeMappingsFromDictionary:listObjectMapping];

listEntityMapping.identificationAttributes = @[ @"listID" ];

执行时我的应用程序崩溃并出现以下错误由于未捕获的异常“NSInternalInconsistencyException”而终止应用程序，原因:“预期字典表示”

请求日志如下:

2014-02-03 13:17:29.789 RKGist[984:70b] T restkit.network:RKObjectRequestOperation.m:178 GET 'http://mydomain.com/api/list/1':
request.headers={
    Accept = "application/json";
    "Accept-Language" = "en;q=1, fr;q=0.9, de;q=0.8, zh-Hans;q=0.7, zh-Hant;q=0.6, ja;q=0.5";
    "User-Agent" = "RKGist/1.0 (iPhone Simulator; iOS 7.0.3; Scale/2.00)";
}
request.body=(null)
2014-02-03 13:17:30.670 RKGist[984:f03] T restkit.network:RKResponseMapperOperation.m:451 Mapping HTTP response to nil target object...
2014-02-03 13:17:30.670 RKGist[984:f03] D restkit.object_mapping:RKMapperOperation.m:377 Executing mapping operation for representation: (
        {
        list =         {
            listID = 1;
            listName = "New List ";
            listSyncStatus = 1;
        };
        tasks =         (
                        {
                listID = 1;
                taskCompletionStatus = 1;
                taskID = 24;
                taskName = "Server Added 2";
                taskSyncStatus = 1;
            },
                        {
                listID = 1;
                taskCompletionStatus = 1;
                taskID = 25;
                taskName = "Server Added 3";
                taskSyncStatus = 1;
            },
                        {
                listID = 1;
                taskCompletionStatus = 1;
                taskID = 23;
                taskName = "Server Added";
                taskSyncStatus = 1;
            }
        );
    }
)
 and targetObject: (null)
2014-02-03 13:17:30.671 RKGist[984:f03] T restkit.object_mapping:RKMapperOperation.m:320 Examining keyPath 'tasks' for mappable content...
2014-02-03 13:17:30.671 RKGist[984:f03] D restkit.object_mapping:RKMapperOperation.m:297 Found mappable collection at keyPath 'tasks': (
        (
                {
            listID = 1;
            taskCompletionStatus = 1;
            taskID = 24;
            taskName = "Server Added 2";
            taskSyncStatus = 1;
        },
                {
            listID = 1;
            taskCompletionStatus = 1;
            taskID = 25;
            taskName = "Server Added 3";
            taskSyncStatus = 1;
        },
                {
            listID = 1;
            taskCompletionStatus = 1;
            taskID = 23;
            taskName = "Server Added";
            taskSyncStatus = 1;
        }
    )
)

日志显示在键路径 tasks 找到可映射集合。

任何人都可以指导我我在这里做错了什么。是我返回的json格式错误还是我的映射代码错误？

Answer 1

您的响应描述符使用 keyPath:@"tasks"。这有效地“挖掘”了响应并忽略了 tasks 部分之外的任何内容。这意味着在映射期间您无权访问 list 部分。

将 addPropertyMapping: 与关系一起使用是为了嵌套映射 - 这不是您所拥有的。您实际上有 2 个单独的部分需要单独映射(因此，2 个响应描述符)以创建所有对象及其关联的 ID(以及连接对象的 ID)。然后，您需要使用外键映射来建立连接(使用 RKConnectionDescription )。

要检查的一件事是返回的 JSON 是什么。看起来好像它可能是 1 个包含对象的大数组，这没有意义。如果它是一个数组，那么您将需要改变您的整个方法。它应该是具有多个键的 1 个对象...