README.md

Two entities with a 1-to-N relationship

This example shows how to create two entities with a 1-to-N relationship. The User entity has many Pet entities, which are related to the User entity.

// factories/UserFactory.ts
export class UserFactory extends Factory<User> {
  ...
  protected attrs(): FactorizedAttrs<User> {
    return {
      ...
      pets: [], // or
      pets: new LazyInstanceAttribute((instance) => new CollectionSubfactory(PetFactory, 1, { owner: instance }))
    }
  }
}

// factories/PetFactory.ts
export class PetFactory extends Factory<Pet> {
  ...
  protected attrs(): FactorizedAttrs<Pet> {
    return {
      ...
      owner: new EagerInstanceAttribute((instance) => new SingleSubfactory(UserFactory, { pets: [instance] })),
    }
  }
}

The Pet entity is the one that has the relation column, so it cannot be created before the User entity. That's why the UserFactory has a LazyInstanceAttribute for the pets attribute, which will create the Pet entities after the User entity is created.

Also, the pets attribute needs to be an array, so we can use here a CollectionSubfactory. The behaviour is similar to SingleSubfactory, but it creates a collection of entities instead of only one.

Some more examples could be found on both test files.