RestKit 0.20 NSCFConstantString valueForUndefinedKey 映射关系时出错

Question

所以我正在尝试将 JSON 与看起来像这样的对象映射

{       
    "item_id": "0",
    "product_id": "217",
    "color_id": "55",
    "size_id": "37",        
    "images": [
        {
            "image_url": "http://www.foo.com/bar.jpg"
        }
    ]
},

我将它直接映射到核心数据实体“项目”。该实体与称为“图像”的实体“图片”具有一对多的关系。实体“图片”有一个 NSString 属性“image_url”。这是我的映射：

- (void) setupPicturesMapping
{
    picturesMapping = [RKEntityMapping mappingForEntityForName:@"Pictures" inManagedObjectStore:self.objectManager.managedObjectStore];

    picturesMapping.identificationAttributes = @[@"image_url"] ;    

    [picturesMapping addAttributeMappingsFromArray:@[@"image_url"]];

    RKResponseDescriptor *responseDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:picturesMapping
                                                                                   pathPattern:@"get_pictures"
                                                                                       keyPath:nil
                                                                                   statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)];
    [self.objectManager addResponseDescriptor:responseDescriptor];
}

- (void) setupItemsMapping
{
itemsMapping = [RKEntityMapping mappingForEntityForName:@"Item" inManagedObjectStore:self.objectManager.managedObjectStore];

itemsMapping.identificationAttributes = @[@"item_id"] ;

[itemsMapping addAttributeMappingsFromArray:@[@"item_id", @"product_id", @"color_id", @"size_id"]];

[itemsMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"images" toKeyPath:@"images" withMapping:picturesMapping]];

RKResponseDescriptor *responseDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:itemsMapping
                                                                                   pathPattern:@"get_items"
                                                                                       keyPath:nil
                                                                                   statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)];
[self.objectManager addResponseDescriptor:responseDescriptor];

}

当我尝试加载项目时出现错误：“由于未捕获的异常 'NSUnknownKeyException' 导致应用程序终止，原因：'[<__nscfconstantstring> valueForUndefinedKey:]：此类不符合键值编码关键 image_url。'"。

有什么问题？

更新：抱歉，第一次贴错代码

Answer 1

我认为您在这里传递了错误的实体名称-

picturesMapping = [RKEntityMapping mappingForEntityForName:@"Pictures" inManagedObjectStore:self.objectManager.managedObjectStore];

传递“图片”而不是“图片”之类-

picturesMapping = [RKEntityMapping mappingForEntityForName:@"Picture" inManagedObjectStore:self.objectManager.managedObjectStore];