求解，怎么用AFNetworking 2.0 发送JSON到服务器请求数据

发送请求：
- (void)sendUpdateUserRequest
{
//添加等待
[MBProgressHUD showHUDWithText:@"正在更新，请稍候···"
toView:selfnavigationControllerview animated:YES];
NSMutableDictionary headDict=[[NSMutableDictionary alloc] init];
NSMutableDictionary dataDict=[[NSMutableDictionary alloc] init];
//组装数据，只是一个例子，可以添加你想要的属性以及值
[headDict setObject:@"user" forKey:@"function"];
[dataDict setObject:_useridLabeltext forKey:@"userid"];
//要发送的数据
NSDictionary jsonDict=[NSDictionary
dictionaryWithObjectsAndKeys:headDict,@"head",dataDict,@"data",nil];
AF>