mysql - Typeorm如何获取关系的关系

Question

我正在使用 entitymanager.findOne 方法获取对象 ChatRoomEntity。 ChatRoomEntity 具有变量 messages，它是 OneToMany - ManyToOne 关系。我选择它没有问题，但是如何获取发送消息的用户。它是 MessageEntity 上具有 OneToMany 关系的变量。

所以基本上我想选择一个房间及其所有消息。但所有消息也应该在 fromUser 上有其值。我选择的房间是这样的:

this.entityManager.findOne(ChatRoomEntity, {where: {id: roomToJoin.id}, relations: ['activeUsers', 'messages']}).then(roomEntity => {
// some code
}

这是我的实体:

用户实体

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

  @CreateDateColumn()
  registrationDate: Date;

  @ManyToMany(type => ChatRoomEntity, room => room.activeUsers, {cascade: true})
  @JoinTable()
  activeChatRooms: ChatRoomEntity[];

  @OneToMany(type => ChatRoomMessageEntity, msg => msg.fromUser)
  chatRoomMessages: ChatRoomMessageEntity[];
}

ChatRoomEntity

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

  @Column('varchar', {nullable: true})
  title: string;

  @OneToMany(type => ChatRoomMessageEntity, chatrmsg => chatrmsg.chatRoom)
  messages: ChatRoomMessageEntity[];

  @ManyToMany(type => UserEntity, user => user.activeChatRooms)
  activeUsers: UserEntity[];

}

ChatRoomMessageEntity

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

  @Column('varchar', {nullable: true})
  message: string;

  @CreateDateColumn()
  creationDate: Date;

  @ManyToOne(type => UserEntity, user => user.chatRoomMessages)
  fromUser: UserEntity;

  @ManyToOne(type => ChatRoomEntity, chatRoom => chatRoom.messages)
  chatRoom: ChatRoomEntity;

}

Answer 1

我们可以通过在 relations 数组本身中使用 'relation.subrelation' 来加载子关系，如下所示:

关系:['relation1', 'relation2', 'relation2.subrelation1']

因此，对于您的情况，您可以简单地执行以下操作，而不是使用 join:

this.entityManager.findOne(ChatRoomEntity, {
        where: {id: roomToJoin.id},
        relations: ['activeUsers', 'messages', 'messages.fromUser'],
      }).then(roomEntity => {
...

此处指定:https://github.com/typeorm/typeorm/blob/master/docs/find-options.md#basic-options