value_support.rb

module Values

  module Support

    def self.included(base)
      base.extend(ClassMethods)
    end

    module ClassMethods
      # Defines a new value_attribute
      #
      # @usage value_attribute :value_menu, Values::Menus::Menu, builder: :from_ar_menu
      #
      # @param [Symbol] value_name
      # @param [Class] value_class
      # @param [Object] options
      # @!macro [attach] value_attribute
      #   @return [$2] the $1 $0
      def value_attribute(value_name, value_class, options = {})

        builder = options[:builder]

        unless value_class < ::Values::Base
          raise ArgumentError.new("You tried to define value accessors for #{value_name} using #{value_class} which does not descend from Values::Base")
        end

        # Defines a setter method that converts your virtus struct into a hash that
        # can be stored in a jsonb column
        define_method(:"#{value_name}=") do |value|
          if value.nil?
            super(value)
          else

            # If a builder has been provided we can call a method provided on the class
            # which will take the provided value and convert it into the value class
            if builder
              value = value_class.send(builder, value)
            end

            unless value.is_a?(value_class)
              raise ArgumentError.new("You tried to set #{value_name} to an instance of #{value.class.name} when it only accepts #{value_class}")
            end

            super(value.to_hash)
          end
        end

        # defines a getter for the value which gets the jsonb field
        # and wraps it in your model
        define_method(value_name) do
          value = super()
          value.present? ? value_class.new(value) : nil
        end
      end
    end
  end
end

value_support_test.rb

require "test_helper"

module Values
  class SupportTest < ActiveSupport::TestCase

    class AValueObject < Values::Base

      values do
        attribute :foo, String
        attribute :bar, String
      end

    end

    # The value_attribute macro works by calling
    # super on active record accessor models, so we need
    # to provide those.
    class PoroBase
      attr_accessor :test

      def foo=(hash)
        @test = hash
      end

      def foo
        @test
      end
    end

    class Poro < PoroBase
      include Values::Support

      value_attribute :foo, AValueObject
    end

    def test_assignment_enforces_type
      poro = Poro.new

      err = -> {
        poro.foo = {}
      }.must_raise ArgumentError

      err.message.must_match /You tried to set foo to/
    end

    def test_assignment_extracts_a_hash
      poro = Poro.new
      foo = Faker::Lorem.word
      bar = Faker::Lorem.word

      poro.foo = AValueObject.new(foo: foo, bar: bar)

      assert_equal poro.test, {foo: foo, bar: bar}
    end

    def test_access_restores_from_a_hash
      poro = Poro.new
      foo = Faker::Lorem.word
      bar = Faker::Lorem.word

      poro.test = {foo: foo, bar: bar}

      assert_equal poro.foo.foo, foo
      assert_equal poro.foo.bar, bar
    end
  end
end