创建多对多关系

创建多对多关系

假设一个 photo 可以放在多个 albums 中，每个 albums 可以包含多个 photo。让我们创建一个Album类：

import { Entity, PrimaryGeneratedColumn, Column, ManyToMany, JoinTable } from "typeorm";

@Entity()
export class Album {
  @PrimaryGeneratedColumn()
  id: number;

  @Column()
  name: string;

  @ManyToMany(type => Photo, photo => photo.albums)
  @JoinTable()
  photos: Photo[];
}

@JoinTable需要指定这是关系的所有者方。

现在添加反向关系到Photo类：

export class Photo {
  /// ... other columns

  @ManyToMany(type => Album, album => album.photos)
  albums: Album[];
}

运行后，ORM 将创建album_photos_photo_albums _联结表。

+-------------+--------------+----------------------------+
|                album_photos_photo_albums                |
+-------------+--------------+----------------------------+
| album_id    | int(11)      | PRIMARY KEY FOREIGN KEY    |
| photo_id    | int(11)      | PRIMARY KEY FOREIGN KEY    |
+-------------+--------------+----------------------------+

记得在 ORM 中使用 ConnectionOptions 注册Album类：

const options: ConnectionOptions = {
  // ... other options
  entities: [Photo, PhotoMetadata, Author, Album]
};

现在让我们将 albums 和 photos 插入我们的数据库:

let connection = await createConnection(options);

// create a few albums
let album1 = new Album();
album1.name = "Bears";
await connection.manager.save(album1);

let album2 = new Album();
album2.name = "Me";
await connection.manager.save(album2);

// create a few photos
let photo = new Photo();
photo.name = "Me and Bears";
photo.description = "I am near polar bears";
photo.filename = "photo-with-bears.jpg";
photo.albums = [album1, album2];
await connection.manager.save(photo);

// now our photo is saved and albums are attached to it
// now lets load them:
const loadedPhoto = await connection.getRepository(Photo).findOne(1, { relations: ["albums"] });

loadedPhoto 如下所示:

{
    id: 1,
    name: "Me and Bears",
    description: "I am near polar bears",
    filename: "photo-with-bears.jpg",
    albums: [{
        id: 1,
        name: "Bears"
    }, {
        id: 2,
        name: "Me"
    }]
}