Rails 4 url_for with host constraint - ruby-on-rails

Question

We created a multi tenancy application with multiple sites and each site is able to modify the routes from a backend.
in routes.rb we load the dynamic routes for all sites and put them into a host constraint like this
routes.rb
Frontend::Application.routes.draw do
DynamicRoutes.load
end
app/models/dynamic_routes.rb
class DynamicRoutes
# dynamically loads the routes from settings into the routes.rb file
# and adds a host constraint to just match with the current sites host
# http://codeconnoisseur.org/ramblings/creating-dynamic-routes-at-runtime-in-rails-4
def self.load
if Site.table_exists?
Frontend::Application.routes.draw do
Site.includes(:setting).each do |site|
site.routes.each do |route|
# write the route with the host constraint
constraints(:host => site.hostname) do
case route[0]
when :shop_show
match "#{route[1]}", to: 'shops#show', via: [:get], as: "shop_show_#{site.id}"
end
end
end
end
end
end
end
# allows to reload the routing
# e.g. when changes in route settings where made
#
def self.reload
Rails.application.reload_routes!
end
end
So we create all routes for each site and match them with a host constraint. This works fine unless we use the url_for helper
#site = Site.find_by(hostname: request.host)
url_for controller: 'shop', action: 'show', host: #site.hostname
url_for returns the first matching url, doesnt matter from which host it should belong to. so the host constraint is not used, even if I put a host: param
Do you have any idea, of how its possible to use url_for with host constraints?

Answer 1

I have had the same task in my application. url_for ignores host param. But we could create additional path helpers in our ApplicationController in the following way:
ApplicationController.rb
%w( shop_show ).each do |helper|
helper_name = "#{helper}_path".to_sym
helper_method helper_name
define_method(helper_name) { |*args| send "#{helper}_#{site.id}_path", *args }
end
After that you are able to use universal path shop_show_path in your views. Of course, you should dynamically assign site variable depending on your host/domain.