Rails and iOS app, authentication question

I want to build web service in Rails 3 and iOS app to work with this service. I need simple thing. User when first time open iOS app, get login screen. When is logged in, iOS app can send and get requests.

I already used Devise for authentication on Rails, and found RESTKit for iOS to map objects and use RESTfull web services, bit I didn't found anything about to confirm to work together.

My question is, 开发者_StackOverflow社区what is the best solution to use on both sides, iOS and RoR to make this to work?

Take a look at what I did for the same setup (IOS device <=> Rails webservice).