0003-immutable-entities-with-events.md

Use Immutable Entities with Domain Events

Status

Accepted

Context

The codebase has two conflicting entity patterns:

• AccountEntity: Immutable, generates domain events internally
• Post: Mutable with dirty flags and complex state tracking

The mutable pattern is harder to test and reason about.

Decision

All entities must follow the immutable pattern with domain events.

Implementation

class Post {
  constructor(
    readonly id: string,
    readonly likeCount: number,
    private events: DomainEvent[] = []
  ) {}

  like(): Post {
    const newPost = new Post(this.id, this.likeCount + 1);
    newPost.events.push(new PostLikedEvent(this.id));
    return newPost;
  }

  pullEvents(): DomainEvent[] {
    return [...this.events];
  }
}