使用AFNetworking 框架 解析数据 报错提示
数据请求失败
Error Domain=NSCocoaErrorDomain Code=3840 "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=0x9b7eba0 {NSDebugDescription=JSON text did not start with array or object and option to allow fragments not set.}
解决：
AFNetWorking的JSON解析默认库是使用的AFJSONRequestOperation模式，只支持text/json，application/json，text/javascript，所以如果出现code=-1016错误则说明当前的JSON解析模式是text/html，所以要加上这段代码：
[AFJSONRequestOperation addAcceptableContentTypes:[NSSet setWithObject:@"text/html"]];//加上这句话

NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:@"%@",kDMBaseURL]];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
[AFJSONRequestOperation addAcceptableContentTypes:[NSSet setWithObject:@"text/html"]];//加上这句话
AFJSONRequestOperation *jsonOperation = [AFJSONRequestOperation JSONRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON) {
DMLog(@"str %@",JSON);
} failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, id JSON) {
DMLog(@"数据请求失败%@",error);
}];
[jsonOperation start];
让他支持text/html模式就可以解决了

数据请求失败
Error Domain=NSCocoaErrorDomain Code=3840 "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=0x9ba1b30 {NSDebugDescription=JSON text did not start with array or object and option to allow fragments not set.}

解决：
后台返回的不是一个有效的JSON string 所以库里面转化的时候一个error就抛出了