Using Rails API for Angular and iOS, with authentication

We have a Rails API that was used with Angular, we previously used the devise angular authentication plugin.

With our new iOS app, we're having difficult trying to figure out how to integrate rails with iOS. There is no plug in for devise and iOS that seems to have active development. Even the angular plugin is not getting much attention.

What's the strategy for approaching a server app implementation with rails, that services both angular and iOS? I believe our problem is more on the client side - how to we drop in code that allows us to make higher level calls and leave the CRUD calls to the other side of the API?