iOS8 App Groups

iOS8 里的App Groups允许应用间相互共享数据，以下有说明：

AppGroup allows data sharing between two different apps or even app and widgets by creating one common shared path (like document directory). Data saved over there can be accessed by any app which is associated with that particular AppGroup. It is an offline data sharing between apps.

用自己的账号测试了一下，在这里创建App Groups（app id 下面）：

然后代码里可通过UserDefaults来调用：

[[NSUserDefaults alloc] initWithSuiteName:@"<group identifier>"];

这里是官方文档，附有使用例子

参考文章：

http://stackoverflow.com/questions/24015506/communicating-and-persisting-data-between-apps-with-app-groups

http://technet.weblineindia.com/mobile/ios-8-app-group/