使用RestKIt在coredata实体上映射json对象

Question

我正在使用RestKit开发一些待办事项列表应用程序。 我面临有关在iOS中使用CoreData返回的json表单服务器的一些映射问题。

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，我将按照该特定列表的Json返回：

`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" ];

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" ];

在执行时， Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Expected a dictionary representation'我的应用崩溃并出现以下错误Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Expected a dictionary representation'

并且请求日志如下：

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;
        }
    )
)

日志说在keypath tasks找到了可映射的集合。

谁能指导我我在这里做错了什么。 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。 这意味着在映射过程中，您无权访问list部分。

使用具有关联关系的addPropertyMapping:用于嵌套映射-这不是您所拥有的。 实际上，您需要单独映射2个单独的部分（因此，需要2个响应描述符）才能创建具有其关联ID（以及连接的对象的ID）的所有对象。 然后，您需要使用外键映射进行连接（使用RKConnectionDescription ）。

要检查的一件事是返回的JSON是什么。 看起来好像是包含一个对象的1个大数组，但这没有任何意义。 如果是数组，则需要更改整个方法 。 它应该是具有多个键的1个对象...