(1.http://www.jianshu.com/p/42516ee26a45
2.http://www.cnblogs.com/kenshincui/p/5644803.html)
http://www.cocoachina.com/ios/20161101/17908.html
http://www.cnblogs.com/kenshincui/p/5644803.html
http://www.cocoachina.com/apple/20160819/17396.html （好文）
http://www.jianshu.com/p/771c65731f37 （好文）
cocoachina 搜索扩展 http://www.cocoachina.com/cms/tags.php?/app%E6%89%A9%E5%B1%95/
https://developer.apple.com/library/content/documentation/General/Conceptual/ExtensibilityPG/Action.html#//apple_ref/doc/uid/TP40014214-CH13-SW1 （官方文档）
