Example of a good service object

user_creator.rb

class UserCreator
  attr_reader :email, :first_name, :last_name
  attr_reader :created_user

  def initialize(email, first_name, last_name)
    @email      = email
    @first_name = first_name
    @last_name  = last_name

    raise ArgumentError, "Missing email" if email.nil?
  end

  def create_user
    check_user_existance
    save_user
  end

  def user_created?
    created_user.present?
  end

  private

  def check_user_existance
    raise "User already exists" if User.exists?(...)
  end

  def save_user
    @created_user = User.create(...)
  end
end