How to access URL helper from rails module

Question

I have a module with a function. It resides in /lib/contact.rb:

module Contact
  class << self
    def run(current_user)
      ...
    end
  end
end

I want to access the URL helpers like 'users_path' inside the module. How do I do that?

Answer 1

Here is how I do it in any context without include

routes = Rails.application.routes.url_helpers
url = routes.some_path

That works in any context. If you're trying to include url_helpers - make sure you are doing that in the right place e.g. this works

module Contact
  class << self
    include Rails.application.routes.url_helpers
  end
end

and this does not work

module Contact
  include Rails.application.routes.url_helpers
  class << self
  end
end

One more example with Capybara tests

feature 'bla-bla' do
  include Rails.application.routes.url_helpers
  path = some_path #unknown local variable some_path
end

and now the right one

include Rails.application.routes.url_helpers
feature 'bla-bla' do
  path = some_path #this is ok
end

Answer 2

Delegation to url_helpers seems much better than including the whole module into your model

delegate :url_helpers, to: 'Rails.application.routes' 
url_helpers.users_url  => 'www.foo.com/users'

reference

Answer 3

I've been struggling with the niceties the helper is expecting from the default controller and stack (default_url_options, etc.), and didn't want to hardcode the host.

Our URL helpers are provided by our nifty module, of course:

include Rails.application.routes.url_helpers

But include this as is, and (1) the helper is going to look for default_url_options, and (2) won't know about the request host nor the request.

The host part comes from the controller instance's url_options. Hence, I pass the controller context into my former module, now a class:

class ApplicationController
  def do_nifty_things
    HasAccessToRoutes.new(self).render
  end
end

class HasAccessToRoutes
  include Rails.application.routes.url_helpers
  delegate :default_url_options, :url_options, to: :@context

  def initialize(context)
    @context = context
  end

  def render
    nifty_things_url
  end
end

Might not fit every case, but it's been useful to me when implementing a sort of custom renderer.

In any way:

• if you want access to the default url options seamlessly, or the host of the request, you need to pass controller/request context in
• if you just need the path, no host, and don't care about the url options, you can just make some dummy methods.

Answer 4

delegate :url_helpers, to: 'Rails.application.routes' 
url_helpers.users_url  => 'www.foo.com/users'

to Augustin Riedinger, that delegation code needs to refer to url_helpers (plural), otherwise you get

undefined method `url_helper'

Answer 5

In your module, just perform a :

 include Rails.application.routes.url_helpers