Using different logic for the same respond_to format in Rails

My Rails application is currently usin开发者_StackOverflow中文版g JSON as the respond_to format for AJAX forms on the site. I'm planning to create a public API for the application, and I'd like to use JSON for it also. How might I distinguish between an AJAX form and an API call in my controllers if the requested format for both is JSON?

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I'd recommend you keep the public api in a separate controller, and have a different route since you say you have different logic. You can have namespaced controllers such as app/controllers/api/users_controller.rb and namespace your routes like:

namespace :admin do
  resources :users
end

and leave your existing controllers with ajax actions used by your site as they are.