Three Examples of DTOs in Ruby - Method 3: Mutable

three_examples_of_dtos_in_ruby_method_3.rb

#
# Mutable DTOs applies in case scenarios where the entire DTO may not be fully
# created in one go. Maybe it needs to be passed around several services and
# gradually enriched before being consumed.
#
# For example, passing around our birthday card to many friends to leave
# messages before finally delivering it to our recipient.
#
class BirthdayCard
  attr_reader :from, :to
  attr_accessor :messages

  def initialize(from:, to:, messages: [])
    @from = from
    @to = to
    @messages = messages
  end

  class Message
    attr_reader :text, :signature

    def initialize(text:, signature:)
      @text = text
      @signature = signature
    end
  end
end

# To create this DTO
birthday_card = BirthdayCard.new(from: 'me', to: 'you')

# Go find Joe in a party and ask him to write something on it
joe_message = BirthdayCard::Message.new(text: 'Happy Birthday!', signature: 'joe_sig.jpeg')
birthday_card.messages << joe_message

# Meet Jane somewhere else and she adds something too
jane_message = BirthdayCard::Message.new(text: 'Happy Birthday!', signature: 'jane_sig.jpeg')
birthday_card.messages << jane_message