Where do API calls go in a ruby on rails MVC framework project?

Where do API calls go in a ruby on rails MVC framework project?

References

Reference NO 1

http://stackoverflow.com/questions/15205613/where-do-api-calls-go-in-a-ruby-on-rails-mvc-framework-project

Reference NO 2

http://guides.rubyonrails.org/getting_started.html

Reference NO 3

http://guides.rubyonrails.org/v2.3.11/getting_started.html

Reference NO 4

http://quizzsystem.comyr.com/web-page/

Reference NO 5

http://jameschambers.com/2012/10/lies-that-ruby-on-rails-people-tell-you/

Reference NO 6

http://sailsjs.org/

Reference NO 7

http://andrzejonsoftware.blogspot.com/2011/09/rails-is-not-mvc.html

Reference NO 8

http://developer.chrome.com/apps/app_frameworks.html