Is there an elegant way using TypeORM to find one record in an array of OneToMany relation and assign it to another field in the entitiy?

问题

I'm looking for a way to implement a function, using NestJS and TypeORM, that will find in OneToMany array a specific element and assign that value to another field in the object. And most important: implemented in a single place in the code.

For example:

The Entity profile have an array of photos, one of the photos is the profile picture. I would like to find that photo in the array and assign it to profilePicture if exist, on every select query. is there a way in typeORM to implement that in a single place in the code?

@Entity('profile')
export class Profile extends BaseEntity {

    @PrimaryGeneratedColumn()
    id: number;

    @OneToMany(type => Photo, photo => photo.profile)
    photos?: Photo[];

    profilePicture?: Photo;
}

回答1:

If you use the query builder, you can achieve that by using leftJoinAndMapOne. I just wanted to add an example, but I just found out that the TypeORM docs already have a good solution for your use case:

 const user = await createQueryBuilder("user")
.leftJoinAndMapOne("user.profilePhoto", "user.photos", "photo", "photo.isForProfile = TRUE")
.where("user.name = :name", { name: "Timber" })
.getOne(); 

Edit: Alternatively you can set the profile in your entity using the Afterload decorator:

@AfterLoad()
private setProfile(): void {
    this.photos.forEach((photo) => {
        if (photo.isForProfile) {
            this.photo = value;
        }
    });
}

来源：https://stackoverflow.com/questions/61407959/is-there-an-elegant-way-using-typeorm-to-find-one-record-in-an-array-of-onetoman