RestKit 添加属性映射和关系映射
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【中文标题】RestKit 添加属性映射和关系映射【英文标题】：RestKit Add Property Mapping and Relationship Mapping 【发布时间】：2014-01-29 11:32:06 【问题描述】：请指导我解决以下问题。
我有两个实体，如下图所示
我在 ios 7 中使用最新版本的 RestKit
现在在我的 appDelegate 中，我正在为“列表”实体使用以下映射
NSDictionary *listObjectMapping = @
@"listID" : @"listID",
@"listName" : @"listName",
@"listSyncStatus" : @"listSyncStatus"
;
RKEntityMapping *listEntityMapping = [RKEntityMapping mappingForEntityForName:@"List" inManagedObjectStore:managedObjectStore];
[listEntityMapping addAttributeMappingsFromDictionary:listObjectMapping];
listEntityMapping.identificationAttributes = @[ @"listID" ];
RKResponseDescriptor *responseDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:listEntityMapping
method:RKRequestMethodGET
pathPattern:@"/api/lists"
keyPath:nil
statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)];
[objectManager addResponseDescriptor:responseDescriptor];
//Inverse mapping, to perform a POST
RKRequestDescriptor *requestDescriptor = [RKRequestDescriptor requestDescriptorWithMapping:[listEntityMapping inverseMapping]
objectClass:[List class]
rootKeyPath:nil
method:RKRequestMethodPOST];
objectManager.requestSerializationMIMEType = RKMIMETypeJSON;
[objectManager setAcceptHeaderWithMIMEType:RKMIMETypeJSON];
[RKMIMETypeSerialization registerClass:[RKNSJSONSerialization class] forMIMEType:@"application/json"];
[objectManager addRequestDescriptor:requestDescriptor];
//Inverse mapping, to perform a PUT
requestDescriptor = [RKRequestDescriptor requestDescriptorWithMapping:[listEntityMapping inverseMapping]
objectClass:[List class]
rootKeyPath:nil
method:RKRequestMethodPUT];
objectManager.requestSerializationMIMEType = RKMIMETypeJSON;
[objectManager setAcceptHeaderWithMIMEType:RKMIMETypeJSON];
[RKMIMETypeSerialization registerClass:[RKNSJSONSerialization class] forMIMEType:@"application/json"];
[objectManager addRequestDescriptor:requestDescriptor];
并为我的任务对象使用以下映射
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" ];
RKResponseDescriptor *taskResponseDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:taskEntityMapping
method:RKRequestMethodGET
pathPattern:@"/api/list/:id"
keyPath:nil
statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)];
[objectManager addResponseDescriptor:taskResponseDescriptor];
//Inverse mapping, to perform a POST
RKRequestDescriptor *taskRequestDescriptor = [RKRequestDescriptor requestDescriptorWithMapping:[taskEntityMapping inverseMapping]
objectClass:[Task class]
rootKeyPath:nil
method:RKRequestMethodPOST];
objectManager.requestSerializationMIMEType = RKMIMETypeJSON;
[objectManager setAcceptHeaderWithMIMEType:RKMIMETypeJSON];
[RKMIMETypeSerialization registerClass:[RKNSJSONSerialization class] forMIMEType:@"application/json"];
[objectManager addRequestDescriptor:taskRequestDescriptor];
//Inverse mapping, to perform a PUT
taskRequestDescriptor = [RKRequestDescriptor requestDescriptorWithMapping:[taskEntityMapping inverseMapping]
objectClass:[Task class]
rootKeyPath:nil
method:RKRequestMethodPUT];
objectManager.requestSerializationMIMEType = RKMIMETypeJSON;
[objectManager setAcceptHeaderWithMIMEType:RKMIMETypeJSON];
[RKMIMETypeSerialization registerClass:[RKNSJSONSerialization class] forMIMEType:@"application/json"];
[objectManager addRequestDescriptor:taskRequestDescriptor];
现在我的问题是如何在这两个实体之间添加关系映射？ 什么是正确的方法？
如果我使用我使用以下代码行
[taskEntityMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"list.listID"
toKeyPath:@"listID"
withMapping:listEntityMapping]];
出现运行时错误，提示“无法为 keyPath listID 添加映射，已存在一个”
如果我用这个
[listEntityMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"listID"
toKeyPath:@"list.listID"
withMapping:taskEntityMapping]];
应用程序因此错误而崩溃实体列表不符合键“列表”的键值编码。'
如果我省略上面的代码并尝试从关系中获取 listID
task.list.listID
它给了我“0”。谁能告诉我我到底做错了什么或者我应该怎么做才能完成上述任务。如果需要，我可以提供更多详细信息。
编辑
但我对所有列表的请求返回以下 json
GET www.mydomain.com/api/lists
[
"listID":"42","listName":"List 4","listSyncStatus":"1",
"listID":"41","listName":"List 3","listSyncStatus":"1",
"listID":"40","listName":"List 2","listSyncStatus":"1"
]
并且对单个列表的请求将返回其任务如下
GET www.mydomain.com/api/list/42
[
"taskID":"22","listID":"42","taskName":"Task 2","taskSyncStatus":"1","taskCompletionStatus":"1",
"taskID":"21","listID":"42","taskName":"Task 1","taskSyncStatus":"1","taskCompletionStatus":"1"
]
即在 json 中返回没有级联关系。这是错误的方式还是我在这里错过了什么？
接受答案后更正
原来我返回了错误的 json，即返回的 json 没有关系，而 iOS 模型有关系“任务”，所以我编辑了我的 rest api 以返回正确的嵌套 json，如下所示
[ "listID" : "96",
"listName" : "List 1",
"listSyncStatus" : "1",
"tasks" : [ "taskCompletionStatus" : "1",
"taskID" : "67",
"taskName" : "Task 2",
"taskSyncStatus" : "1"
,
"taskCompletionStatus" : "1",
"taskID" : "66",
"taskName" : "Task 1",
"taskSyncStatus" : "1"
]
,
"listID" : "97",
"listName" : "List 2",
"listSyncStatus" : "1",
"tasks" : [ "taskCompletionStatus" : "1",
"taskID" : "69",
"taskName" : "Task 1",
"taskSyncStatus" : "1"
,
"taskCompletionStatus" : "1",
"taskID" : "68",
"taskName" : "Task 1",
"taskSyncStatus" : "1"
]
]
返回嵌套的 json 之后，一切都像魅力一样，特别是这一行
[listEntityMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"tasks"
toKeyPath:@"tasks"
withMapping:taskEntityMapping]];
希望这有助于像我这样的人掌握关系概念。
【问题讨论】：
【参考方案1】：你的模态图表明你有一对多的关系（一个列表有很多任务）。
据我所知，在这种情况下，您只需要在 List 实体上添加关系映射，不需要在 Task 实体上。同样对于一对多关系，您不需要在Task实体下添加list关系。
您的实体关系应如下所示
所以尝试关注
[listEntityMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"YOUR_JSON_KEYPATH_HERE" toKeyPath:@"tasks" withMapping: taskEntityMapping]];
重要
以上方法
FromKeyPath parameter 应该是您的 JSON key 的名称，关系开始的地方。
toKeyPath parameter 应该是你在实体图中提到的relationship name。 IE; tasks。
withMapping应该是多个实体的映射。在你的情况下taskEntityMapping
希望这能解决问题。
【讨论】：
iOS 建议应该有反比关系。 @Umair，谢谢你是对的:)。删除反向关系的建议是，尽可能少地编写代码。这样调试就很容易了。如果现在一切正常，您可以根据需要添加反向关系。这就是我喜欢调试我的代码的方式:)【参考方案2】：不知道为什么这不起作用，但您可以尝试像这样创建关系映射：
[taskEntityMapping addConnectionForRelationship:@"list" connectedBy:@ @"listId": @"listId" ];
[listEntityMapping addConnectionForRelationship:@"tasks" connectedBy:@ @"listId":@"listId"];
【讨论】：
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