Rails 5.x: How can I add a route at runtime without overwriting original routes table?

Question

Say I have a controller action that should result in a new route being added to the routes table:

def make_route
  vanity_url = params[:vanity_url]
  vanity_redirect = params[:vanity_redirect]
  return render json: { status: 400 } unless vanity_url && vanity_redirect

  Rails.application.routes.draw do
    get vanity_url, to: redirect(vanity_redirect)
  end
  render json: { status: :ok }
end

When I trigger this action, it does add the new route but completely erases the rest of the table! How do I prepend, append or otherwise map through the original routes when drawing the new table?

Answer 1

In prod's env Rails load configuration once and not listen to changes. If you want to build custom routes you must reload routes each time when the new route was added:

Rails.application.reload_routes!

Also, that does not append a new route to your route file and any server restart reset your router to default. But you can save new routes to the database and recreate them when the server starts or build your routes inside routes.rb from ENV variables.

But if you want to use draw and need a new route just once:

Rails.application.routes.disable_clear_and_finalize = true  #add this line
Rails.application.routes.draw do
  #new route
end