Show 403 page for CanCan Access Denied

gistfile1.rb

# app/controllers/application_controller.rb
class ApplicationController < ActionController::Base

  rescue_from CanCan::AccessDenied do |exception|
    # Make sure we don't redirect to an HTML page
    # in API requests because this is absolutely a bad idea
    unless request.accept == 'application/json'
      # Solutions in order of preference:
      # # Solution #1: Show a full page with Access Denied
      # render(:file => File.join(Rails.root, 'public/403.html'), :status => 403, :layout => false)
      # # Solution #2: Redirect to home page and show a flash message
      # flash[:error] = "Access denied."
      # redirect_to root_url
    end
  end
end