Custom devise Strategy

subdomain_authenticatable.rb

#require 'devise/strategies/authenticatable'

module SubdomainAuthenticatable
    # Default strategy for signing in a user, based on his email and password in the database.
    class CustomStrategy < Devise::Strategies::Authenticatable
      def authenticate!
        resource = valid_password?  && mapping.to.joins(:company).where(authentication_hash.merge({:companies => {:subdomain => "test"}})).first
        return fail(:not_found_in_database) unless resource

        if validate(resource){ resource.valid_password?(password) }
          resource.after_database_authentication
          success!(resource)
        end
      end
    end
end

Warden::Strategies.add(:subdomain_authenticatable, SubdomainAuthenticatable::CustomStrategy)

Devise.add_module(:subdomain_authenticatable,
  :strategy => true,
  :controller => :sessions,
  :route => :session
  )