Idea for simple and dynamic error page.

error_pages.rb

class ErrorPages < Ambulance::App

  # idea 0: rails' rescue_from
  rescue_from CanCan::AccessDenied, ActiveRecord::NotFound, ActionController::RoutingError do |exception|
    render file: 'public/404.html', status: :not_found, layout: false
  end

  # idea 1:
  routes ActiveRecord::NotFound,
         ActionController::RoutingError, to: 404

  # or you can also use symbol.
  routes ActiveRecord::NotFound,
         ActionController::RoutingError, to: :not_found

  routes CanCan::AccessDenied, to: :unauthorized
  routes StandardError,        to: :internal_server_error

  # idea 2:
  map :not_found,
    ActiveRecord::NotFound, ActionController::RoutingError

  map :unauthorized,
    CanCan::AccessDenied

  map :internal_server_error, StandardError

  handle :not_found do |exception|
    render file: "public/404.html"
  end

  handle :internal_server_error do |exception|
    render file: "public/500.html"
  end

  # or give a block directly(applicable to both).
  map :not_found, exceptions do
    render file: "public/404.html"
  end

  routes exceptions, to: :not_found do
    render file: "public/404.html"
  end
end