maigun_connector.rb

require 'singleton'

class MailgunConnector
  include Singleton

  attr_reader :api_key

  def client(api_key=settings.mailgun_key)
  	if @api_key == api_key && @api_key
  	  @client
  	else
  	  @api_key = api_key
  	  @client = Mailgun::Client.new(@api_key)
  	end   
  end 	

  def domain
  	@domain || change_domain
  end

  def change_domain(name=settings.mailgun_domain)  
  	@domain = name
  end	

end  

MailgunConnector.instance.client
MailgunConnector.instance.domain