Behaviour and macros for Domain-Driven Design Aggregate Roots.

An aggregate is a consistency boundary: the root is the only entry point, and nested entities are stored inside it (one row for the whole aggregate). Aggregates collect domain events; the repository persists them with the state.

Same rules as DDD.Entity (field rules, invariant, defop, sealing).

Usage

defmodule MyApp.Order do
  use DDD.Aggregate

  aggregate do
    identity :id,          :uuid
    field    :customer_id, :string, required: true
    field    :status,      :atom, default: :pending
    field    :items,       {:list, MyApp.OrderItem}, default: []

    invariant MyApp.Specs.MaxItems, max: 10
  end

  defop confirm(order), requires: MyApp.Specs.OrderIsPending do
    order
    |> Map.put(:status, :confirmed)
    |> emit_event(MyApp.Events.OrderConfirmed.new(%{order_id: order.id}))
  end
end

Events emitted inside a defop are discarded when the result is invalid.

Nested types: {:list, EntityModule} and {:one, EntityModule}.