Using EntityRepository instead of EntityManager

Entity Repositories are thin layers on top of EntityManager. They act as an extension point, so we can add custom methods, or even alter the existing ones. The default, EntityRepository implementation just forwards the calls to underlying EntityManager instance.

EntityRepository class carries the entity type, so we do not have to pass it to every find or findOne calls.

const booksRepository = em.getRepository(Book);

const books = await booksRepository.find({ author: '...' }, {
  populate: ['author'],
  limit: 1,
  offset: 2,
  orderBy: { title: QueryOrder.DESC },
});

console.log(books); // Book[]

Note that there is no such thing as "flushing repository" - it is just a shortcut to em.flush(). In other words, we always flush the whole Unit of Work, not just a single entity that this repository represents.

Custom Repository

info

Since v4, we need to make sure we are working with correctly typed EntityRepository to have access to driver specific methods (like createQueryBuilder()). Use the one exported from your driver package.

To use custom repository, just extend EntityRepository<T> class:

import { EntityRepository } from '@mikro-orm/mysql'; // or any other driver package

export class CustomAuthorRepository extends EntityRepository<Author> {

  // custom methods...
  public findAndUpdate(...) {
    // ...
  }

}

And register the repository via @Entity decorator:

@Entity({ customRepository: () => CustomAuthorRepository })
export class Author {
  // ...
}

@Repository() decorator has been removed in v5, use @Entity({ customRepository: () => MyRepository }) instead.

Note that we need to pass that repository reference inside a callback so we will not run into circular dependency issues when using entity references inside that repository.

Now we can access our custom repository via em.getRepository() method.

Inferring custom repository type

To have the em.getRepository() method return correctly typed custom repository instead of the generic EntityRepository<T>, we can use EntityRepositoryType symbol:

@Entity({ customRepository: () => AuthorRepository })
export class Author {

  [EntityRepositoryType]?: AuthorRepository;

}

const repo = em.getRepository(Author); // repo has type AuthorRepository

We can also register custom base repository (for all entities where we do not specify customRepository) globally, via MikroORM.init({ entityRepository: CustomBaseRepository }).

For more examples, take a look at tests/EntityManager.mongo.test.ts or tests/EntityManager.mysql.test.ts.