how to create web service Api in rails 4?

can anyone help me how to create a web service API in rails 4. I know how create web service API in ruby 1.8.7 and rails 2.3.5 with action web service gem. When I am trying to use http://ift.tt/1Mts3iY gem in rails 4, I am getting deprecated errors.I want to upgrade my web service app. Please help me.

Thanks in advance.