SDWebImage 的安装（转自官方文档）

Installation

There are two ways to use this in your project: copy all the files into your project, or import the project as a static library.

Add the SDWebImage project to your project

• Download and unzip the last version of the framework from the download page
• Right-click on the project navigator and select "Add Files to "Your Project":
• In the dialog, select SDWebImage.framework:
• Check the "Copy items into destination group's folder (if needed)" checkbox

Add dependencies

• In you application project app’s target settings, find the "Build Phases" section and open the "Link Binary With Libraries" block:
• Click the "+" button again and select the "ImageIO.framework", this is needed by the progressive download feature:

Add Linker Flag

Open the "Build Settings" tab, in the "Linking" section, locate the "Other Linker Flags" setting and add the "-ObjC" flag:

Import headers in your source files

In the source files where you need to use the library, import the header file:

#import <SDWebImage/UIImageView+WebCache.h>

Build Project

At this point your workspace should build without error. If you are having problem, post to the Issue and the community can help you solve it.