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Aggregate Generator

acc-create-aggregate

Generates DDD Aggregates for PHP 8.5. Creates consistency boundaries with root entity, domain events, and invariant protection. Includes unit tests.

SKILL.md

Full skill instructions

Aggregate Generator

Generate DDD-compliant Aggregates with root, domain events, and tests.

Aggregate Characteristics

  • Consistency boundary: All changes atomic
  • Root entity: Single entry point
  • Transactional consistency: Invariants always valid
  • Domain events: Records what happened
  • Encapsulation: Children accessed through root
  • Identity: Referenced by root ID

Generation Process

Step 1: Generate Base AggregateRoot

Path: src/​Domain/​Shared/​Aggregate/

  1. AggregateRoot.php — Base class with event recording

Step 2: Generate Aggregate Root Entity

Path: src/​Domain/​{BoundedContext}/​Entity/

  1. {Name}.php — Main aggregate root

Step 3: Generate Child Entities (if needed)

Path: src/​Domain/​{BoundedContext}/​Entity/

  1. {ChildName}.php — Child entity inside aggregate

Step 4: Generate Domain Events

Path: src/​Domain/​{BoundedContext}/​Event/

  1. {Name}CreatedEvent.php
  2. {Name}{Action}Event.php for each behavior

Step 5: Generate Tests

Path: tests/​Unit/​Domain/​{BoundedContext}/​Entity/


File Placement

ComponentPath
Base AggregateRootsrc/​Domain/​Shared/​Aggregate/
Aggregate Entitysrc/​Domain/​{BoundedContext}/​Entity/
Child Entitiessrc/​Domain/​{BoundedContext}/​Entity/
Domain Eventssrc/​Domain/​{BoundedContext}/​Event/
Unit Teststests/​Unit/​Domain/​{BoundedContext}/​Entity/

Naming Conventions

ComponentPatternExample
Aggregate Root{Name}Order
Child Entity{Parent}{Name}OrderLine
Created Event{Name}CreatedEventOrderCreatedEvent
State Event{Name}{Action}EventOrderConfirmedEvent

Quick Template Reference

Base AggregateRoot

abstract class AggregateRoot
{
    private array $events = [];

    protected function recordEvent(DomainEvent $event): void
    {
        $this->events[] = $event;
    }

    public function releaseEvents(): array
    {
        $events = $this->events;
        $this->events = [];
        return $events;
    }
}

Aggregate Root Entity

final class {Name} extends AggregateRoot
{
    private {Name}Status $status;

    private function __construct(
        private readonly {Name}Id $id,
        {properties}
    ) {
        $this->status = {Name}Status::Draft;
    }

    public static function create({Name}Id $id, {params}): self
    {
        $aggregate = new self($id, {args});

        $aggregate->recordEvent(new {Name}CreatedEvent(...));

        return $aggregate;
    }

    public function {behavior}({params}): void
    {
        $this->ensureValidState();
        // Apply change
        $this->recordEvent(new {Name}{Behavior}Event(...));
    }
}

Child Entity

final readonly class {ChildName}
{
    public function __construct(
        public {PropertyType} $property1,
        public {PropertyType} $property2
    ) {}

    public function total(): Money
    {
        return $this->unitPrice->multiply($this->quantity);
    }
}

Design Rules

RuleGoodBad
Transaction BoundaryOne aggregate per transactionMultiple aggregates
ReferenceBy ID onlyFull entity reference
SizeSmall, focusedLarge with many collections
InvariantsAlways validCan be in invalid state
EventsRecord all state changesNo event recording

Anti-patterns to Avoid

Anti-patternProblemSolution
Large AggregatePerformance issuesSplit into smaller aggregates
Entity ReferencesTight couplingUse IDs only
Public SettersNo invariant protectionUse behavior methods
Missing EventsCan't track historyRecord event for each change
No RootMultiple entry pointsSingle root entity

References

For complete PHP templates and examples, see:

  • references/​templates.md — AggregateRoot, Entity, Child Entity, Test templates
  • references/​examples.md — Order aggregate with OrderLine, events, and tests

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