blog_rails_api_auth_pt_2_4.rb

# routes.rb

constraints AuthenticatedConstraint.new do
  resources :widgets, only: :index
end

# app/constraints/authenticated_constraint.rb

class AuthenticatedConstraint
  def matches?(request)
    warden = request.env['warden']
    warden && warden.authenticate!(:token_authentication_strategy)
  end
end

Warden::Strategies.add(:token_authentication_strategy,
                       TokenAuthenticationStrategy)