gistfile1.rb

class UsersController < ApplicationController
  def create
    respond_to do |format|
      format.html do
        @user = UserService.create(params[:user], true)
        redirect_to @user
      end
      format.json do
        @user = UserService.create(params[:user], false)
        render :json => @user,
          :status => :created,
          :location => @user
      end
    end
  end
end

class UserService
  def self.create(attributes, welcome)
    user = User.new(attributes)
    user.save
    EmailService.welcome_email(user) if welcome
    user
  end
end

class EmailService
  def self.welcome_email(user)
    email = UserMailer.welcome_email user
    email.deliver
  end
end