ios - Restkit 在嵌套外键关系中使用@parent

Question

我在使用 RestKit 建立一些关系时遇到了最困难的时期。

从item到venue之间存在一对多关系，但通过多个级别的关系。

这是 JSON 结构的概要:

{
    "id": 1, 
    "name": "Venue Name", 
    "sections": [
        {
            "id": 1, 
            "name": "Paper", 
            "categories": [
                {
                    "id": 1, 
                    "name": "Paper Goods", 
                    "items": [
                        {
                            "venue" : 1
                            // Other data goes here
                        }
                }
         }
}

我正在尝试将 venue 外键连接到 Venue 的 id 属性。

我已尝试执行以下操作:

NSEntityDescription * itemEntity = [NSEntityDescription entityForName:@"DSItem" inManagedObjectContext:managedObjectStore.mainQueueManagedObjectContext];
NSRelationshipDescription * venueRel = [itemEntity relationshipsByName][@"venue"];
RKConnectionDescription * connection = [[RKConnectionDescription alloc] initWithRelationship:venueRel attributes:@{@"venue" : @"pk"}]; // id --> pk on DSVenue class

但对象映射后 field 属性为nil。

如何在其中使用@parent来创建外键关系？或者有更好的方法吗？

类似于:

@{@"@parent.@parent.@parent.pk" : @"venue"}

我看过this这是一个问题，但它似乎适用于将属性链接到父属性，而不是将外键链接到实体。

任何帮助将不胜感激!

编辑:这是所有的映射代码

RKEntityMapping *itemMapping = [RKEntityMapping mappingForEntityForName:@"DSItem" inManagedObjectStore:managedObjectStore];
itemMapping.identificationAttributes = [DSItem identificationAttributes];
[itemMapping addAttributeMappingsFromDictionary:[DSItem attributeMappings]];

NSEntityDescription * itemEntity = [NSEntityDescription entityForName:@"DSItem" inManagedObjectContext:managedObjectStore.mainQueueManagedObjectContext];
NSRelationshipDescription * venueRel = [itemEntity relationshipsByName][@"venue"];
RKConnectionDescription * connection = [[RKConnectionDescription alloc] initWithRelationship:venueRel keyPath:@"venue"];

[itemMapping addConnection:connection];

RKEntityMapping *categoryMapping = [RKEntityMapping mappingForEntityForName:@"DSCategory" inManagedObjectStore:managedObjectStore];
categoryMapping.identificationAttributes = [DSCategory identificationAttributes];
[categoryMapping addAttributeMappingsFromDictionary:[DSCategory attributeMappings]];
[categoryMapping addRelationshipMappingWithSourceKeyPath:@"items" mapping:itemMapping];

RKEntityMapping *sectionMapping = [RKEntityMapping mappingForEntityForName:@"DSSection" inManagedObjectStore:managedObjectStore];
sectionMapping.identificationAttributes = [DSSection identificationAttributes];
[sectionMapping addAttributeMappingsFromDictionary:[DSSection attributeMappings]];
[sectionMapping addRelationshipMappingWithSourceKeyPath:@"categories" mapping:categoryMapping];

RKEntityMapping *venueMapping = [RKEntityMapping mappingForEntityForName:@"DSVenue" inManagedObjectStore:managedObjectStore];
[venueMapping addAttributeMappingsFromDictionary:[DSVenue attributeMappings]];
venueMapping.identificationAttributes = [DSVenue identificationAttributes];
[venueMapping addRelationshipMappingWithSourceKeyPath:@"sections" mapping:sectionMapping];

RKResponseDescriptor *venueDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:venueMapping
                                                                                     method:RKRequestMethodGET
                                                                                pathPattern:[DSVenue pathPattern]
                                                                                    keyPath:[DSVenue keyPath]
                                                                                statusCodes:successIndexSet];


RKResponseDescriptor *itemDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:itemMapping
                                                                                    method:RKRequestMethodGET
                                                                               pathPattern:[DSItem pathPattern]
                                                                                   keyPath:[DSItem keyPath]
                                                                               statusCodes:successIndexSet];

[manager addResponseDescriptorsFromArray:@[itemDescriptor, venueDescriptor]];

Answer 1

只是不要做你想做的事。您的映射看起来很好，假设您在模型中配置了反向关系，您只需从项目实体导航关系即可到达关联的 field 实体。

也就是说，我认为 @parent.id 引用应该可以使连接成为可能(通过授予对 id 的访问权限)。但话又说回来，确实不需要。您可以获取模型并对其进行预测，以获取您所拥有的关系所需的任何信息。