Event Store

A full-blown event store is beyond the scope of this documentation, but Codefy has an InMemoryEventStore we can use. It implements the EventStore interface that consists of two methods: append, getAggregateHistoryFor, and loadFromPlayhead. We won’t be concerning ourselves with the third method in this documentation.

An append/commit should always be transactional. The whole set of DomainEvents should be persisted, or none at all.

The EventStore supports two read operations. One that fetches an aggregates complete history and the other that fetches a history from a version point.

Let’s test it out:

<?php

use App\Domain\Post\Post;
use App\Domain\Post\ValueObject\PostId;
use App\Domain\Post\ValueObject\Title;
use App\Domain\Post\ValueObject\Content;
use Codefy\Domain\EventSourcing\InMemoryEventStore;

use function expect;
use function it;
use function iterator_to_array;

it('should retrieve all events from the event store based on aggregate id.', function () {
    $postId = new PostId(value: '1cf57c2c-5c82-45a0-8a42-f0b725cfc42f');

    $post = Post::createPost(
        postId: $postId,
        title: new Title(value: 'Second Post Title'),
        content: new Content(value: 'Another short form content.')
    );

    $events = $post->getRecordedEvents();
    $eventStore = new InMemoryEventStore();

    foreach ($events as $event) {
        $eventStore->append(event: $event);
    }

    $iterator = $eventStore->getAggregateHistoryFor(
        aggregateId: PostId::fromString(
            postId: '1cf57c2c-5c82-45a0-8a42-f0b725cfc42f'
        )
    );
    $aggregateHistory = iterator_to_array(iterator: $iterator->getIterator());

    foreach ($aggregateHistory as $event) {
        expect(value: $post->title())->toEqual(expected: $event->title());
        expect(value: $post->aggregateId())->toEqual(expected: $event->aggregateId());
    }
});

An in-memory implementation of EventStore is on Github.

If you have any questions or issues, please feel free to post to the Documentation Forum.

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