RestKit - 与 CoreData 的关系映射 - 响应错误答案

【问题标题】：RestKit - Relashionship Mapping with CoreData - Response ErrorRestKit - 与 CoreData 的关系映射 - 响应错误
【发布时间】：2014-02-14 20:15:15
【问题描述】：

我有一个来宾实体，内部来宾是一个城市实体。我已经使用 RKRelationshipMapping 在 CoreData 和 RestKit 中设置了关系。

我已经正确映射了一个实体，但是当我使用 RKRelationshipMapping 添加一个城市实体时，在使用 @"cityId" 属性调用以下方法时似乎会生成此错误：

-[RKPropertyInspector classForPropertyNamed:ofEntity:]: unrecognized selector sent to instance

我的映射代码：

RKObjectManager *objectManager   = [RKObjectManager managerWithBaseURL:[NSURL URLWithString:self.serverBaseAddress]];
    objectManager.managedObjectStore = [RKManagedObjectStore defaultStore];

    [RKObjectManager setSharedManager:objectManager];

    RKEntityMapping *cityEMapping = [RKEntityMapping mappingForEntityForName:self.cityEntityName inManagedObjectStore:[RKManagedObjectStore defaultStore]];
    [cityEMapping addAttributeMappingsFromDictionary:@{
                                                        @"id"    : @"cityId",
                                                        @"name"  : @"name"
                                                        }];

    RKEntityMapping *guestEMapping = [RKEntityMapping mappingForEntityForName:self.entityName inManagedObjectStore:[RKManagedObjectStore defaultStore]];
    [guestEMapping addAttributeMappingsFromDictionary:@{
                                                        @"name"     : @"name",
                                                        @"photo"    : @"photo",
                                                        @"comment"  : @"comment",
                                                        @"id"       : @"guestId",
                                                        @"date"     : @"date"
                                                        }];

    [guestEMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"city"
                                                                                  toKeyPath:@"city"
                                                                                withMapping:cityEMapping]];

    guestEMapping.identificationAttributes = @[ @"guestId" ];

    RKResponseDescriptor *responseDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:guestEMapping method:RKRequestMethodAny pathPattern:self.postGetAddress keyPath:nil statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)];
    [objectManager addResponseDescriptor:responseDescriptor];

以及应用停止的位置：（propertyClass 在 propertyClass = [[RKPropertyInspector sharedInspector]...中接收 0x00）

- (Class)classForKeyPath:(NSString *)keyPath
{
    NSArray *components = [keyPath componentsSeparatedByString:@"."];
    Class propertyClass = self.objectClass;
    for (NSString *property in components) {
        propertyClass = [[RKPropertyInspector sharedInspector] classForPropertyNamed:property ofClass:propertyClass isPrimitive:nil]; 
        if (! propertyClass) propertyClass = [[RKPropertyInspector sharedInspector] classForPropertyNamed:property ofEntity:self.entity];
        if (! propertyClass) break;
    }

    return propertyClass;
}

这是json：

    [{"id":"3","name":"Convidado3","city":{"id":"2","name":"SÃ£o Paulo"},"date":"Data2","comment":"comentario3","photo":":P"},
     {"id":"2","name":"Convidado2","city":{"id":"1","name":"Rio de Janeiro"},"date":"Data2","comment":"comentario2","photo":":|"},
     {"id":"1","name":"Convidado1","city":{"id":"1","name":"Rio de Janeiro"},"date":"Data1","comment":"comentario1","photo":":)"},
     {"id":"5","name":"Convidado5","city":{"id":"4","name":"VitÃ³ria"},"date":"Data4","comment":"comentario5","photo":":K"},
     {"id":"4","name":"Convidado4","city":{"id":"3","name":"Belo Horizonte"},"date":"Data3","comment":"comentario4","photo":";)"}]

实体Guest有一个名为city的关系，它通过一个名为guests的关系以下列方式连接到City实体：
客人.....城市
城市>客人

如果我只是删除它工作正常的关系，没有城市子对象... 任何帮助或建议表示赞赏...

【问题讨论】：

您不会错过城市地图中的标识属性吗？
您是否正确设置了链接器值？
好的，我已经在城市映射中添加了标识属性（在RKEntityMapping *cityEMapping之后），cityEMapping.identificationAttributes = @[ @"cityId" ];现在错误在其他地方：static NSArray *RKArrayOfAttributesForEntityFromAttributesOrNames(NSEntityDescription *entity, NSArray *attributesOrNames)...我可以看到来宾实体和它有一个以 NSRelationshipDescription 作为值的城市属性。但是当代码运行时NSAttributeDescription *attribute = [[entity attributesByName] valueForKey:attributeOrName]; 属性仍然接收 nil... 这会引发NSException
Wain，链接器值是什么意思？只是为了帮助澄清我是如何获得当前代码的，我一直在关注link，关系部分代码...

标签： objective-c core-data restkit

【解决方案1】：

我已经解决了这个问题：

在调试完所有步骤后，我更改了以下行

发件人：

RKEntityMapping *cityEMapping = [RKEntityMapping mappingForEntityForName:self.cityEntityName inManagedObjectStore:[RKManagedObjectStore defaultStore]];

收件人：

RKEntityMapping *cityEMapping = [RKEntityMapping mappingForEntityForName:@"City" inManagedObjectStore:[RKManagedObjectStore defaultStore]];

它成功了！

我不明白这个问题，因为我在调试期间检查了 self.cityEntityName 的值，它是 @"City"，所以从技术上讲它应该可以工作。至于线路：

RKEntityMapping *guestEMapping = [RKEntityMapping mappingForEntityForName:self.entityName inManagedObjectStore:[RKManagedObjectStore defaultStore]];

工作得很好...没有任何变化，我不知道该说什么。感谢您的建议。

【讨论】：