class User
  attr_accessor :first_name, :last_name

  def initialize(first_name = nil, last_name = nil)
    @first_name = first_name
    @last_name = last_name
  end

  def to_s
    puts "firstname: #{first_name} lastname: #{last_name}"
  end


end

# User.new('John', 'Doe')

class UserBuilder
  def initialize
    @user = User.new(:John, :Doe)
  end

  def build
    @user
  end

  def first_name(first_name = nil)
    @user.first_name = first_name if first_name
    self
  end

  def last_name(last_name = nil)
    @user.last_name = last_name if last_name
    self
  end

end


UserBuilder.new.first_name.last_name("test").build.to_s