数据返回的一个字符串类型的 不是json类型

  AFHTTPSessionManager *manager =  [AFHTTPSessionManager manager];
     manager.responseSerializer = [AFHTTPResponseSerializer serializer];
    NSString *str = [NSString stringWithFormat:HuXingBaoMingChoice,_appdelegate.uuid,_detaiLID];
    
    [manager GET:str parameters:nil progress:^(NSProgress * _Nonnull downloadProgress) {
        
    } success:^(NSURLSessionDataTask * _Nonnull task, id  _Nullable responseObject) {
        NSString *string = [[NSString alloc] initWithData:responseObject encoding:NSUTF8StringEncoding];
        self.textContent  = [string copy];
      
    } failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
    
    }];