Ruby: Immutable Value Object with Struct

ruby_immutable_value_object_with_struct.md

Ruby: Immutable Value Object with Struct

Freezing the initializer after passing the args to super makes the object immutable.

# frozen_string_literal: true

# Freezing the initializer after passing the args to `super` makes the object immutable.
#
# Example:
#
#   require 'value_object'
#
#   ForcePullData = Struct.new(:repository_name, :site_id, keyword_init: true) do
#     include ValueObject
#   end
#
#   data = ForcePullData.new(repository_name: 'sandbox', site_id: 'site-id')
#
#   > data.repository_name
#   => "sandbox"
#
#   > data.repository_name = "plaything"
#   FrozenError: can't modify frozen ForcePullData:
#   #<struct ForcePullData repository_name="sandbox", site_id="site-id">
module ValueObject
  def initialize(**args)
    super(args)
    freeze
  end
end

This trick comes from Polished Ruby Programming by Jeremy Evans.