AFHTTPRequestOperationManager *mgr = [AFHTTPRequestOperationManager manager];
// responseObject的类型是NSXMLParser
mgr.responseSerializer = [AFXMLParserResponseSerializer serializer];
// responseObject的类型是NSData
mgr.responseSerializer = [AFHTTPResponseSerializer serializer];
//服务器返回的是JSON数据
mgr.responseSerializer = [AFJSONResponseSerializer serializer];
是要设置的,否则报错.默认JSON.
AFHTTPRequestOperationManager的那些事
原文：http://www.cnblogs.com/iOS771722918/p/4444014.html