現場でDDD持ち帰ってやってみたのRuby実装

main.rb

# https://little-hands.hatenablog.com/entry/2019/05/11/genba-ddd-handson
# 上記のブログ記事に触発されてRubyでの実装を試してみました。
# 本当はCapacityPlanとOptionPlanのデータをMinitest外で宣言したかったのですが、
# Minitestから参照できなかったのでsetupで宣言しています。

class Price
  def initialize(value)
    raise "value should be greater than or equal to 0. given value:#{value}" unless value >= 0
    @value = value
  end

  def to_i
    @value
  end

  def plus(price)
    Price.new(value + price)
  end
end

class Plans < Array
  def [](id)
    find { |item| item.id_eq?(id) }
  end
end

class CapacityPlan
  def initialize(id, price)
    @id = id
    @price = Price.new(price)
  end

  def to_s
    @id.to_s
  end

  def id_eq?(id)
    @id == id
  end

  def self.seed
    Plans.new([
      CapacityPlan.new(:_1GB, 1000),
      CapacityPlan.new(:_3GB, 3000),
      CapacityPlan.new(:_30GB, 6000)
    ]);
  end
end

class OptionPlan
  def initialize(id, price, permitted_capacity_plans)
    @id = id
    @price = Price.new(price)
    @permitted_capacity_plans = permitted_capacity_plans
  end

  def permitted?(capacity_plan)
    @permitted_capacity_plans.contains(capacity_plan)
  end

  def id_eq?(id)
    @id == id
  end

  def self.seed
    Plans.new([
      OptionPlan.new(:movie_free, 1000, [:_3GB, :_30GB]),
      OptionPlan.new(:call_free, 3000, [:_1GB, :_3GB, :_30GB])
    ]);
  end
end

class PlanValidator
  def initialize(capacity_plan, option_plans = [])
    @capacity_plan = capacity_plan
    @option_plans = option_plans
  end

  def valid?
    return true if @option_plans.empty?
    @option_plans.any? { |option_plan| option_plan.permit?(@capacity_plan) }
  end

  def validate!
    raise "Unpermitted capacity_plan:#{@capacity_plan} given" unless valid?
  end
end

class Contract
  def initialize(capacity_plan, option_plans = [])
    PlanValidator.new(capacity_plan, option_plans).validate!
    @capacity_plan = capacity_plan
    @option_plans = option_plans
  end
end

require 'minitest/autorun'

class TestContract < Minitest::Test
  def setup
    @capacity_plans = CapacityPlan.seed
    @option_plans = OptionPlan.seed
  end

  def test_valid_1GB_without_options
    Contract.new(@capacity_plans[:_1GB], [])
  end

  def test_invalid_1GB_with_movie_free
    assert_raises do
      Contract.new(@capacity_plans[:_1GB], [@option_plans[:movie_free]])
    end
  end
end