Rails – How to use a Helper Inside a Controller

You can use

• helpers.<helper> in Rails 5+ (or ActionController::Base.helpers.<helper>)
• view_context.<helper> (Rails 4 & 3) (WARNING: this instantiates a new view instance per call)
• @template.<helper> (Rails 2)
• include helper in a singleton class and then singleton.helper
• include the helper in the controller (WARNING: will make all helper methods into controller actions)