App Extensions

Using URLs to bring users into our app, and even to a specific feature, is a very handy feature. But it does mean leaving the app the user was in and coming over to ours. Throughout the history of iOS, each app has lived in its own sandbox, prohibited from directly interacting with other apps. Each app has its own section of the filesystem and can’t see anything outside its folders. Each app runs in its own process and cannot share resources like frameworks or dynamic libraries. This can lead to a lot of duplication of effort across apps.

Recent versions of iOS have poked some holes in the walls between applications by allowing apps to create app extensions. From the user’s point of view, extensions are packaged with an app and ...

Get iOS 9 SDK Development now with the O’Reilly learning platform.

O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.