TypeORM 如何在不加载关系实体的情况下访问引用关系字段

Question

As we know, to create ManyToOne/OneToMany relation we have to use @ManyToOne/@OneToMany decorators on a field.

In my project I have two entities: Project and Position .

This is how I created a relation:

@Entity('positions')
export class Position {

  @ManyToOne(() => Project, {
    nullable: false,
    eager: true,
  })
  @JoinColumn()
  project: Project;

}

TypeORM documentation says this code will create projectId FOREIGN KEY column in the database and store a project id in it.

Then when we trying to access project property TypeORM loads a project by the id stored in projectId field.

QUESTION

How can I access that pojectId field without loading a relational entity?

The property projectId does not exists by default in Position entity and if I manually create it it is not populated by projectId column value.

I have tried this way:

  @ManyToOne(() => Project, {
    nullable: false,
    eager: false,
  })
  @JoinColumn()
  project: Project;

  projectId: string;

Answer 1

You can use the @RelationId decorator exported by typeorm . Using your example:

import {
  Column,
  Entity,
  ManyToOne,
  RelationId,
  JoinColumn,
} from 'typeorm'

@Entity()
export class Position {
  @ManyToOne(() => Project, {
    nullable: false,
    eager: false,
  })
  @JoinColumn()
  project: Project;

  @Column()
  @RelationId((position: Position) => position.project)
  projectId: string;
}