ios - 使用 RestKit 对象映射空响应

Question

感谢 help here在 RestKit 邮件列表上，我已经能够解析我的 JSON，但现在我遇到了一个新问题，解析一个空响应。下面是我的查询有结果时 JSON 的样子:

    {"blobsList":
        {"blobs":
            [   
                {"createdOn":"2012-03-16T15:13:12.551Z","description":"Fake description ","hint":"And a useless hint","id":400,"name":"Fake CA one","publicId":"FF6","type":0},

                {"createdOn":"2012-03-16T17:33:48.514Z","description":"No hint on this one, but it does have a description.","hint":"Hint","id":402,"name":"Second fake one in CA","publicId":"FF8","type":0}
            ]}}

所以我将其添加到我的映射中:

        RKObjectMapping* blobsListMapping = [RKObjectMapping mappingForClass:[GetResponseInRegionResponseList class]];
        [blobsListMapping mapKeyPath:@"blobsList" toAttribute:@"blobsList"];

        [[RKObjectManager sharedManager].mappingProvider setMapping:blobMapping forKeyPath:@"blobsList.blobs"];

        [[RKObjectManager sharedManager].mappingProvider setMapping:blobsListMapping forKeyPath:@"blobsList"];

我的类(class)是:

        @interface GetResponseInRegionResponse : NSObject
        {
            NSString* name;
            NSString* blobId;
            NSString* description;
            NSString* hint;
        }


        @interface GetResponseInRegionResponseList : NSObject
        {
            NSArray  *blobsList;
        }

但现在问题是我的服务器也可以为 JSON 返回这个:

        {"blobsList":""} 

是的，如果查询没有结果，我会返回。它使我的应用程序崩溃

        restkit.object_mapping:RKObjectMapper.m:255 Performing object mapping sourceObject: {
            blobsList = "";
        }
         and targetObject: (null)

        2012-03-22 11:56:16.233 Ferret[7399:17a07] T restkit.object_mapping:RKObjectMapper.m:269 Examining keyPath 'blobs' for mappable content...
        2012-03-22 11:56:16.233 Ferret[7399:17a07] D restkit.object_mapping:RKObjectMapper.m:279 Found unmappable value at keyPath: blobs
        2012-03-22 11:56:16.233 Ferret[7399:17a07] T restkit.object_mapping:RKObjectMapper.m:269 Examining keyPath 'blobsList.blobs' for mappable content...
        2012-03-22 11:56:16.239 Ferret[7399:17a07] *** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<__NSCFConstantString 0xdb1d0> valueForUndefinedKey:]: this class is not key value coding-compliant for the key blobs.'

所以我试图想出一种方法让 ResKit 映射这个空响应。我已经尝试了所有这些:

[[RKObjectManager sharedManager].mappingProvider setMapping:blobListMapping forKeyPath:@"blobsList"];
[[RKObjectManager sharedManager].mappingProvider setMapping:NULL forKeyPath:@"blobsList"];
[blobListMapping mapKeyPath:@"" toAttribute:@"blobsList"];
[blobListMapping mapKeyPath:@"blobsList" toAttribute:@"blobsList"];

但是他们都崩溃了。我正在尝试制作源代码的正面和反面，“此类不是关键 blob 的键值编码兼容”令人费解，因为那里没有任何 blob，只有 blobsList。感谢您的帮助，谢谢!

Answer 1

我在我的项目中遇到了类似的事情。我正在发布到一个网络服务，该服务将我发布的对象返回给我，该对象包装在一个数组中。这导致 RestKit 在解析时崩溃，因为它期望只返回一个对象而不是一个集合。为了解决这个问题，我实现了 objectLoader:willMapData: delegate 方法并将响应对象从数组中拉出并通过 RestKit 解析发送该对象，一切都很好。

也许您可以做类似的事情。检查您是否在 blobslist 中取回了一个字符串并将其转换为一个空数组，然后再通过 RestKit 解析发送它。

- (void)objectLoader:(RKObjectLoader *)objectLoader willMapData:(id *)mappableData
{
    // Horrible hack to convert posted object that gets returned as an array into a single object
    // that can be mapped.
    //
    if ([objectLoader.targetObject isKindOfClass:[TSLPostPostContract class]])
    {
        if ([*mappableData isKindOfClass:[NSArray class]])
        {
            *mappableData = [*mappableData objectAtIndex:0];
        }
    }
}