Behaviour and macros for Domain-Driven Design Value Objects.

Value objects are immutable, identity-less and defined entirely by their attributes: two value objects with the same attributes are equal. They are built only through new/1, which runs field rules and specification invariants.

Usage

defmodule MyApp.Money do
  use DDD.ValueObject

  value_object do
    field :amount,   :decimal, required: true
    field :currency, :string,  required: true

    validate :amount,   &(Decimal.compare(&1, 0) == :gt), message: "must be positive"
    validate :currency, &(String.length(&1) == 3),        message: "must be 3-letter ISO code"
  end
end

{:ok, money} = MyApp.Money.new(amount: Decimal.new("10.00"), currency: "USD")