Undefined instance method "respond_to" in Rails 5 API Controller
ActionController::API does not include the ActionController::MimeResponds module. If you want to use respond_to you need to include MimeResponds.
class ApplicationController < ActionController::API include ActionController::MimeRespondsendclass Api::MyController < ApplicationController def method1 # ... respond_to do |format| format.xml { render(xml: "fdsfds") } format.json { render(json: "fdsfdsfd" ) } end endendSource: ActionController::API docs
As of Rails 4.2, this functionality no longer ships with Rails, but can easily be included with the responders gem (like Max noted in comments above).
Add gem 'responders' to your Gemfile, then
$ bundle install$ rails g responders:installSources:
http://edgeguides.rubyonrails.org/4_2_release_notes.html#respond-with-class-level-respond-tohttps://github.com/plataformatec/responders