gistfile1.rb

class CreateUserAccount
  
  def self.build
    self.new(SendWelcomeEmail.build, TrackRegistration.build)
  end
  
  def initialize(send_welcome_email, track_registration)
    @send_welcome_email = send_welcome_email
    @track_registration = track_registration
  end
  
  def perform(arg1, arg2)
    ...
  end
end

class CreateUserAccount
  class SendWelcomeEmail
    
    def self.build
      self.new
    end
    
    def perform(arg1, arg2)
      ...
    end
  end
end

class CreateUserAccount
  class TrackRegistration
    
    def self.build
      self.new
    end
    
    def perform(arg1)
      ...
    end
  end
end