AFNetworking
AFNetworking is a delightful networking library for iOS, macOS, watchOS, and tvOS. It's built on top of the Foundation URL Loading System, extending the powerful high-level networking abstractions built into Cocoa. It has a modular architecture with well-designed, feature-rich APIs that are a joy to use.
Perhaps the most important feature of all, however, is the amazing community of developers who use and contribute to AFNetworking every day. AFNetworking powers some of the most popular and critically-acclaimed apps on the iPhone, iPad, and Mac.
引用GitHub上的介绍，AFNetworking是基于Foundation URL Loading System设计，是对NSURLSession的高度集中封装，使其简单易用。
AFNetworking主要由以下几部分组成：
AFURLSessionManager-AFNetworking的核心，用于管理NSURLSession，生成NSURLSessionTask以及处理NSURLSessionDelegate等代理回调。
AFHTTPSessionManager-继承自AFURLSessionManager，专门用于HTTP连接。
AFNetworkReachabilityManager-网络连接检测
AFSecurityPolicy-处理HTTPS证书信任等
AFURLRequestSerialization-序列化客户端的请求NSURLRequest
AFURLResponseSerialization-序列化服务端的响应NSURLResponse
AFNetworking相关文章：
[AFNetworking]一、简介
[AFNetworking]二、AFURLSessionManager
[AFNetworking]三、AFHTTPSessionManager
[AFNetworking]四、AFURLRequestSerialization
[AFNetworking]五、AFURLResponseSerialization
