Rails/iPhone: recommended place of doing OAuth

I'm building a (Rails-based) web service with a mobile app (iPhone) as frontend. In order to allow people to login using Facebook, I've built something using devise and omniauth that allows the user to log in using Facebook and store the credentials in the database. This works perfectly, all from the web app.

However, now the second part: I want to let users log in via the mobile app. Of course, there are the FB Connect libraries, but they give the mobile app access to the Graph API. Instead, I would like a mobile log-in screen that authorizes Rails to access the data. This is because later on, users might 开发者_StackOverflowuse both the iPhone app and web app.

What would be the recommended way of doing this? Are there any best practices?

I solved it by doing the authorization using FB Connect and the FB app. After authorizing, the FB app opens my app again, and I can read out the access token. Which I can then send to the server and use there.