The operation couldn’t be completed. (Cocoa error 3840.)" (JSON text did not start with array or object and option to allow fragments not set.) UserInfo=0x1d87a2c0 {NSDebugDescription=JSON text did not start with array or object and option to allow fragments not set.}

问题是我应该在哪里设置AFNetworking 2.0中的允许片段？

更新：

我的类是AFHTTPSessionManager的子类.我已经创建了一个JSONResponseSerializer,它也不起作用.

返回的JSON如下：

[{"StoryId":1,"Title":"The big red dog","Abstract":"There was a big red dog and the dog was very big","IsFeatured":true}]
 
-(instancetype) initWithBaseURL:(NSURL *)url
{
    NSURL *base = [NSURL URLWithString:@"URL to the web service that returns the json"];
    self = [super initWithBaseURL:base];
 
    AFJSONResponseSerializer *responseSerializer = [AFJSONResponseSerializer serializerWithReadingOptions:NSJSONReadingAllowFragments];
 
    [self setResponseSerializer:responseSerializer];
 
    return self;
}

返回的错误如下：

[0] (null)  @"NSDebugDescription" : @"Invalid value around character 0."

来自WEB服务器的响应：

[{"StoryId":1,"IsFeatured":true}]

来自WEB服务器的响应状态：

HTTP/1.1 200 OK
Server: Microsoft-IIS/7.0
X-Powered-By: ASP.NET
Content-Type: application/json;charset=utf-8
X-AspNetMvc-Version: 3.0
Connection: close
Date: Mon,28 Oct 2013 20:02:21 GMT
Content-Length: 121
Cache-Control: private
X-AspNet-Version: 4.0.30319
 
[{"StoryId":1,"IsFeatured":true}]