Method add

packages/core/src/entity/Collection.ts:236–266

Adds one or more items to the collection, propagating the change to the inverse side. Returns the number of items added.

(
    entity: TT | Reference<TT> | Iterable<TT | Reference<TT>>,
    ...entities: (T | Reference<T>)[]
  )

  /** Adds one or more items to the collection, propagating the change to the inverse side. Returns the number of items added. */
  add<TT extends T>(
    entity: TT | Reference<TT> | Iterable<TT | Reference<TT>>,
    ...entities: (T | Reference<T>)[]
  ): number {
    entities = (Utils.asArray(entity) as (T | Reference<T>)[]).concat(entities);
    const unwrapped = entities.map(i => Reference.unwrapReference(i)) as T[];
    this.validateModification(unwrapped);
    const em = this.getEntityManager(entities as T[], false);
    let added = 0;

    for (const item of entities) {
      const entity = Reference.unwrapReference(item) as T;

      if (!this.contains(entity, false)) {
        this.incrementCount(1);
        this[this.#items.size] = entity;
        this.#items.add(entity);
        added++;
        this.#dirty = true;
        this.propagate(entity, 'add');
      }
    }

    if (this.property.kind === ReferenceKind.ONE_TO_MANY && em) {
      em.persist(entities);
    }

    this.cancelOrphanRemoval(unwrapped);

    return added;
  }

  /**
   * Remove specified item(s) from the collection. Note that removing item from collection does not necessarily imply deleting the target entity,