How to insert an entity with OneToMany relation in NestJS?

Question

There is the description how to do this in typeorm official docs https://typeorm.io/#/many-to-one-one-to-many-relations. But I can't do the same in NestJS with Repository and insert method.

I have written these entities (other columns were omitted)

@Entity()
export class News {
  @OneToMany(type => NewsImage, image => image.news)
  public images: NewsImage[];
}

@Entity()
export class NewsImage {
  @ManyToOne(type => News, news => news.images)
  public news: News;
}

I have tried something like this

function first() {
  const news = new News();
  const image = new NewsImage();
  news.images = [ image ];
  return from(this.newsRepo.insert(news))
    .pipe(
      switchMap(() => this.imageRepo.insert(image)),
    );
}

function second() {
  const news = new News();
  const image = new NewsImage();
  image.news = news;
  return from(this.imageRepo.insert(image))
    .pipe(
      switchMap(() => this.newsRepo.insert(news)),
    )
}

It inserts news and image, but image's newsId is null.

Answer 1

Check cascade property

@Entity()
export class News {
  @OneToMany(type => NewsImage, image => image.news, { cascade: ['insert', 'update'] })
  public images: NewsImage[];
}

Then if you do something like

let news = {
        images: [{
            date: "",
            etc: ""
        }],
        title: ""
    }

If then you call this.repository.save(news) it will save the news and the images. And updates too. Check more docs about this on typeorm docs.

Answer 2

Declaring new News() creates a new entity but does not save it to the database. You first need to insert or .save() the news object and then add it to image.

async function first() {
  // you can .save() it however you want, the point is it must be saved to the db
  const news = await News.create({ title: 'Async rules the world' }).save()
  const image = new NewsImage()
  image.news = news // now news has an id from the database
  // ...
}