App-Extension.md

App Extension

App Extension Programming Guide

1. App Extensions Increase Your Impact

2. Understand How an App Extension Works

3. Creating an App Extension

3.1. Begin Development By Choosing the Right Extension Point

3.2. Examine the Default App Extension Template

3.3. Respond to the Host App’s Request

如果你的 extension app 需要一些时间来执行长时间的任务，比如上传大的内容到网站。需要用NSURLSession启动一个后台的上传过程。因为后台的上传需要一个单独的进程，这个上传过程能在 extension app 完成宿主app的请求并且销毁后，还能以低优先级继续执行。Performing Uploads and Downloads

3.4. Optimize Efficiency and Performance

3.5. Design a Streamlined UI

3.6. Ensure Your iOS App Extension Works on All Devices

3.7. Debug, Profile, and Test Your App Extension

3.8. Distribute the Containing App

4. Handling Common Scenarios

4.1. Using an Embedded Framework to Share Code