gistfile1.rb

# /controller/users_controller.rb
class UsersController < ApplicationController
#código
  def create
    @user = User.new(params[:user])
    respond_to do |format|
      if @user.save
        flash[:notice] = "User #{@user.name} was successfully created."
        # Basta incluir esta unica linha.
        Confirmation.deliver_confirmation_for_email(@user)
        format.html { redirect_to(:action=>:index) }
        format.xml { render :xml => @user, :status => :created, :location => @user }
      else
        format.html { render :action => "new" }
        format.xml { render :xml => @user.errors, :status => :unprocessable_entity }
      end
    end
  end
#código
end