如何在TypeORM中一次添加多个关系

Question

So i've been struggling with this for some time now, i have this many to many realtionship in my codebase. Between a User and Odds. I want the User to be able to add an Odds

User Entity:

 @Entity()
    @Unique(['username'])
    export class User extends BaseEntity {
      @PrimaryGeneratedColumn()
      id: number;

      @Column()
      username: string;

      @Unique(['email'])
      @Column()
      email: string;

      @Column()
      password: string;

      @Column({ nullable: true })
      customerId: string;

      @ManyToMany(type => Odds, odds => odds.user)
      @JoinTable()
      odds: Odds[];

      @Column()
      salt: string;

      async validatePassword(password: string): Promise<boolean> {
      const hash = await bcrypt.hash(password, this.salt);
      return hash === this.password;
  }
}

Odds Entity:

@Entity()
export class Odds extends BaseEntity {
  @PrimaryGeneratedColumn()
  id: number;

  @Column()
  hometeam: string;

  @Column()
  awayteam: string;

  @Column()
  hometeamLogo: string;

  @Column()
  awayteamLogo: string;

  @Column()
  bet: string;

  @Column({ type: 'real' })
  value: string;

  @Column()
  stake: number;

  @Column({ type: 'real' })
  bookieOdds: string;

  @ManyToMany(type => User, user => user.odds)
  user: User[];
}

When i try to add a relation like this

async addOddsToUser(user: User, oddsId: number): Promise<void> {
    const id = user.id;
    const userDB = await this.userRepository.findOne({ id });
    const odds = await this.oddsRepository.findOne({ id: oddsId });
    userDB.odds = [odds];
    userDB.save();
  }

In the associative table it does add the relation the first time, but if i add one more it overrides the first relation, i also tried userDB.odds.push(odds); which doesnt work.

Any help would be appreciated!

Answer 1

The Problem is that your addOddsToUser function overrides the userDB.odds array with a new single array item each time. Thus existing relations will be deleted as mentioned in the FAQ :

When you save the object it will check if there are any categories in the database bind to the question - and it will detach all of them. Why? Because relation equal to [] or any items inside it will be considered like something was removed from it, there is no other way to check if an object was removed from entity or not.

Therefore, saving an object like this will bring you problems - it will remove all previously set categories.