iOS实用开源代码推荐(二) 本篇相对第一篇来讲，更加实用，主要是一些很基础的工具，经过改造已经融入到自家的框架之中。
1.SDWebImage
Asynchronous image downloader with cache support with an UIImageView category
简单几行代码就可以解决图片异步下载，缓存的问题，可以直接用到代码中，可以大大节约时间。
https://github.com/lipeiqiang/SDWebImage
2.MBProgressHUD
MBProgressHUD + Customizations
MBProgressHUD is an iOS drop-in class that displays a translucent HUD with an indicator and/or labels while work is being done in a background thread. The HUD is meant as a replacement for the undocumented, private UIKit UIProgressHUD with some additional features.
https://github.com/jdg/MBProgressHUD
3.InAppSettingsKit
This iPhone framework allows settings to be in-app in addition to being in the Settings app
程序内设置很容易被实现，大大节约开放时间，并且非常灵活。
https://github.com/futuretap/InAppSettingsKit
4.Nimbus
来自于Three20，文档很丰富。
https://github.com/jverkoey/nimbus
5.AFNetworking
轻量级的Network Framework，支持iOS和Mac。
https://github.com/AFNetworking/AFNetworking