Ruby on Rails 4.2 with android same feature CRUD

Hi i am currently doing a project and i need more info on how to make a login using android , into my ruby on rails 4.2 webapp

i have already looked into this

but this is made from RoR3 and i need something really updated as i have been using 4.2 and i need to make an android app that can do some crud

I am using devise for the login so i need something that i can use for the android that can make the connections , and doing the job for the basic CRUD.

I need tutorials that can really help me and thanks!