Three Examples of DTOs in Ruby - Method 2: Hierarchical

three_examples_of_dtos_in_ruby_method_2.rb

#
# There are two classes here belonging to the same data transfer object
# They follow the first example, but are hierarcal. Meaning that the DTO called
# BirthdayCard has a sub-DTO called BirthdayCard::Template.
#
# It is possible to have more deeply nested hiearcies within
# BirthdayCard::Template depending on the use-case.
#
# Finally, if the DTO becomes overly-complex, i.e. say BirthdayCard had 3 layers
# of hiearchy, and more than one branch:
#
# - BirthdayCard::Message
# - BirthdayCard::Message::Text
# - BirthdayCard::Message::Signature
# - BirthdayCard::Template
# - BirthdayCard::Template::Title
# - BirthdayCard::Template::Picture
# ... etc
#
# It would be best to have a separate service (outside the Domain logic) assemble it
#
class BirthdayCard
  attr_reader :from, :to, :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
joe_message = BirthdayCard::Message.new(text: 'Happy Birthday!', signature: 'joe_sig.jpeg')
jane_message = BirthdayCard::Message.new(text: 'Happy Birthday!', signature: 'jane_sig.jpeg')
BirthdayCard.new(from: 'me',
                 to: 'you',
                 messages: [joe_message, jane_message])