使用 RestKIt 在核心数据实体中映射 json 对象
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【中文标题】使用 RestKIt 在核心数据实体中映射 json 对象【英文标题】：Mapping json object on coredata entity using RestKIt 【发布时间】：2014-02-03 08:28:17 【问题描述】：我正在使用 RestKit 开发一些待办事项列表应用程序。我在ios中使用CoreData返回的json表单服务器面临一些映射问题。
情景
以下是我正在使用的列表和任务实体的图像。
当有人向服务器上的列表添加新任务时，我返回该特定列表的以下 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" ];
而我的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，我的应用程序崩溃并出现以下错误
Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Expected a dictionary representation'
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？
【问题讨论】：
【参考方案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法访问list 部分。
将addPropertyMapping: 与关系一起用于嵌套映射 - 这不是您所拥有的。实际上，您有 2 个单独的部分需要单独映射（因此，2 个响应描述符）以创建具有关联 ID（以及连接对象的 ID）的所有对象。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 个包含对象的大型数组，这没有任何意义。如果它是一个数组，那么您将需要更改整个方法。它应该是 1 个带有多个键的对象...
【讨论】：
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