Decorating entities

Use @Seed() on any entity property to describe how it should be populated. Plain column properties (scalars) take a factory function; relation properties take the bare decorator (or a count option for collections).

import { Entity, PrimaryGeneratedColumn, Column, OneToMany, ManyToOne } from 'typeorm'
import { faker } from '@faker-js/faker'
import { Seed } from '@joakimbugge/typeorm-seeder'

@Entity()
class Author {
  @PrimaryGeneratedColumn()
  id!: number

  @Seed(() => faker.person.fullName())
  @Column()
  name!: string

  @Seed({ count: 3 })
  @OneToMany(() => Book, (b) => b.author)
  books!: Book[]
}

@Entity()
class Book {
  @PrimaryGeneratedColumn()
  id!: number

  @Seed(() => faker.lorem.words(4))
  @Column()
  title!: string

  @Seed()
  @ManyToOne(() => Author, (a) => a.books)
  author!: Author
}

Using the sequence index

Every factory receives a zero-based index as its third argument. When called from createMany or saveMany, the index counts up across the batch — useful for generating unique sequential values:

@Seed((_, __, i) => `user-${i}@example.com`)
@Column()
email!: string

When called from create or save (single entity), the index is always 0.

Circular relations

When seeding Author, its books are seeded too. Each Book has an author relation back to Author — but seeding that would loop back to Author, which would seed more books, and so on forever.

typeorm-seeder breaks the cycle at the point where a type would re-enter itself. In the example above, book.author is left undefined when seeding from Author. Seeding a Book directly works fine and does populate book.author — the cycle only cuts when a type is already being seeded higher up in the same chain.