gistfile1.rb

module UrlHelper

  def generate_my_url(obj)
    my_path({ :obj_id => obj.slug })
  end
  
  # [..]

end

class MyCell < Cell::Rails
  helper UrlHelper
  
  # [..]

end

# cell template

link_to "My Link", generate_my_url(obj) # -> Missing host to link to! Please provide :host parameter or set default_url_options[:host]
link_to "My Link", my_path({ :obj_id => obj.slug }) # -> works

gistfile2.rb

class MyController < ApplicationController
  include UrlHelper
  
  def my_action
    
    redirect_to generate_my_url(@obj) and return # -> works
    redirect_to my_path({ :obj_id => @obj.slug }) and return # -> works

    render :some_other_action
    
  end

  # [..]

end