How to change URL used in accept_invitation_url dynamically in Devise Invitable?

I'm using Devise invitable for invitation. We're using different sub-domains like, test1.domain.com, test2.domain.com etc in a single rails app and would like the invitation url we send to users to reflect that.

Since the value seems to be based on the config var in config/production.rb:

config.action_mailer.default_url_options = { host: 'www.domain.com' }

It's not clear to me what the best way to change the url that used in the email view:

<%= link_to t("devise.mailer.invitation_instructions.accept"), accept_invitation_url(@resource, :invitation_token => @token) %>

I could not find the source of the accept_invitation_url so I'm not even sure where that is set.

Any help is greatly appreciated!

Solution

Rookie mistake:

The trick was to stop trying to search for this as an devise invitable question and more of a general ActionMailer question which led me to this simple solution: http://excid3.com/blog/change-actionmailer-email-url-host-dynamically/

Basically just reset the url in the application controller with any logic you want:

 before_filter :set_mailer_host

 def set_mailer_host
    ActionMailer::Base.default_url_options[:host] = request.host_with_port
 end