如何使用 RestKit 将对象 POST 到 Rails？

Question

我正在尝试使用 RestKit 和 Rails 来实现奇迹。我正在使用 Rails 3.1.1 和 RestKit 0.9.3 （不是 master 分支）。我在 iOS 应用程序中使用 Core Data，因此我尝试将应用程序设置为使用尽可能多的 RestKit 魔法来与 Rails 应用程序交互。

但是，我在尝试将新对象发布到要创建的服务器时遇到问题。我已经成功地获取了这些对象。这是我执行此操作的代码：

RKObjectManager* manager = [RKObjectManager objectManagerWithBaseURL:@"http://IP_ADDRESS"];
manager.objectStore = [RKManagedObjectStore objectStoreWithStoreFilename:@"magikarp.sqlite"];
manager.client.requestQueue.showsNetworkActivityIndicatorWhenBusy = YES;
manager.acceptMIMEType = RKMIMETypeJSON; 
manager.serializationMIMEType = RKMIMETypeJSON; 

///
/// Setup Routing
///

RKObjectRouter *router = [[RKObjectRouter alloc] init];
[router routeClass:[List class] toResourcePath:@"/lists/(listID)"];
[router routeClass:[List class] toResourcePath:@"/lists" forMethod:RKRequestMethodPOST];
manager.router = router;

///
/// Setup mapping for my "List" object; a subclass of NSManagedObject
///
RKManagedObjectMapping *listMapping = [RKManagedObjectMapping mappingForClass:[List class]];
listMapping.primaryKeyAttribute = @"listID";

[listMapping mapAttributes:@"title", nil];
[listMapping mapKeyPath:@"id" toAttribute:@"listID"];
[manager.mappingProvider setMapping:listMapping forKeyPath:@"list"];

这似乎对我来说效果很好。现在，我想将新创建的对象发布回服务器。

- (void)createList:(NSString *)listName {
    List *newList = [List object];
    newList.title = listName;
    [[RKObjectManager sharedManager] postObject:newList delegate:self]; 
}

我使用我希望新列表具有的名称来调用此方法。调用此方法，但出现此错误：

2011-12-06 19:24:17.822 Magikarp[13921:14c1b] W restkit.object_mapping:RKObjectMapper.m:74 Adding mapping error: Could not find an object mapping for keyPath: ''
2011-12-06 19:24:17.823 Magikarp[13921:14c1b] E restkit.network:RKObjectLoader.m:190 Encountered errors during mapping: Could not find an object mapping for keyPath: ''
2011-12-06 19:24:17.823 Magikarp[13921:14c1b] Hit error: Error Domain=org.restkit.RestKit.ErrorDomain Code=1001 "Could not find an object mapping for keyPath: ''" UserInfo=0x6bb9da0 {=RKObjectMapperKeyPath, NSLocalizedDescription=Could not find an object mapping for keyPath: ''}

我为完成映射所做的尝试是：（

RKObjectMapping *listSerializationMapping = [RKObjectMapping mappingForClass:[NSMutableDictionary class]];
[listSerializationMapping mapKeyPath:@"title" toAttribute:@"title"];
[listSerializationMapping mapKeyPath:@"ListID" toAttribute:@"id"];
[manager.mappingProvider setSerializationMapping:listSerializationMapping forClass:[List class]];

这给出了上述错误）。我知道有一种非常简单的方法可以做到这一点，但是没有一个示例具有此代码，并且所有文档似乎都已过时...您是否也必须将信息作为 POST 参数发送？帮助将不胜感激，谢谢！

更新
这是服务器响应 - 它可以工作，但参数似乎有点混乱？ （我输入的标题是：“由 iPhone 2 制造！”）

Started POST "/lists" for 129.21.86.32 at 2011-12-07 09:34:43 -0500
  Processing by ListsController#create as JSON
  Parameters: {"id"=>0, "title"=>"Made from the iPhone 2!", "list"=>{"id"=>0, "title"=>"Made from the iPhone 2!"}}
WARNING: Can't verify CSRF token authenticity
WARNING: Can't mass-assign protected attributes: id
   (0.3ms)  BEGIN
  SQL (0.9ms)  INSERT INTO "lists" ("created_at", "title", "updated_at") VALUES ($1, $2, $3) RETURNING "id"  [["created_at", Wed, 07 Dec 2011 14:34:43 UTC +00:00], ["title", "Made from the iPhone 2!"], ["updated_at", Wed, 07 Dec 2011 14:34:43 UTC +00:00]]
   (16.4ms)  COMMIT
Completed 201 Created in 77ms (Views: 1.8ms | ActiveRecord: 21.9ms)

Answer 1

我认为 inverseMapping 选择器应该足以进行序列化映射

RKManagedObjectMapping *listMapping = [RKManagedObjectMapping mappingForClass:[List class]];
listMapping.primaryKeyAttribute = @"listID";

[listMapping mapAttributes:@"title", nil];
[listMapping mapKeyPath:@"id" toAttribute:@"listID"];
[manager.mappingProvider setMapping:listMapping forKeyPath:@"list"];
//this should be enough
[manager.mappingProvider setSerializationMapping:[listMapping inverseMapping] forClass:[List class]];

编辑：

根据我们的聊天对话，RestKit 产生的警告是由于服务器响应缺少根 KeyPath （返回为裸数组）。为了解决这个问题，我们需要告诉 RestKit 使用特定的映射来映射响应：

mapping = [[[RKObjectManager sharedManager] mappingProvider] mappingForKeyPath:@"list"];
[[RKObjectManager sharedManager] postObject:newList mapResponseWith:mapping delegate:self];

Answer 2

这是来自 RestKit 文档。有一个方便的方法可以设置映射和序列化映射，

[[RKObjectManager sharedManager].mappingProvider registerMapping:mapping withRootKeyPath:@"person"];

这将为您调用 setMapping:forKeyPath: ，然后生成序列化映射并设置根 keyPath 。