自引用多对多关系类型ORM [英] Self-Referencing ManyToMany Relationship TypeORM

问题描述

我刚刚开始使用 TypeORM，我正在努力让以下关系发挥作用:

I have just started using TypeORM and I'm struggling getting the following relationship to work:

User->Friends，而朋友也是用户对象.我的吸气剂，getFriends &然而，getFriendsInverse 正在工作；我现在想区分这两者.换句话说;当我执行 mysql join 时，我不想在朋友上做一个左连接，在 inverseFriends 上做另一个.

User->Friends, whereas a Friend is also a User Object. My getters, getFriends & getFriendsInverse are working, however; I do now want to distinguish between the two. In other words; when I perform a mysql join I do not want to do a left join on friends and another one on inverseFriends.

getter getFriends() 需要返回所有朋友，无论我在对象的哪一边".

The getter getFriends() needs to return all friends, regardless of which "side" the object I'm on.

有意义吗?

这是我的模型定义:

getFriends() {
    // This method should also return inverseFriends;
    // I do not want to return the concat version; this should
    // happen on the database/orm level
    // So I dont want: this.friends.concat(this.inverseFriends) 
    return this.friends;
}

@ManyToMany(type => User, user => user.friendsInverse, {
    cascadeInsert: false,
    cascadeUpdate: false,
})
@JoinTable()
friends = [];

@ManyToMany(type => User, user => user.friends, {
    cascadeInsert: true,
    cascadeUpdate: true,
    cascadeRemove: false,
})
friendsInverse = [];

我希望有人理解我的问题 :D谢谢马特

I hope someone understands my question :D Thanks Matt

推荐答案

您可以自行参考您的关系.这是一个简单的有向图示例(也就是一个节点可以有一个父节点和多个子节点).

You can self-reference your relations. Here is an example of a simple directed graph (aka a node can have a parent and multiple children).

@Entity()
export class Service extends BaseEntity {

  @PrimaryGeneratedColumn()
  id: number;
  
  @Column()
  @Index({ unique: true })
  title: string;

  @ManyToOne(type => Service, service => service.children)
  parent: Service;

  @OneToMany(type => Service, service => service.parent)
  children: Service[];
}

要记住的一个重要注意事项是，当使用 find* 函数从数据库读取对象时，这些关系不会自动加载.

An important note to keep in mind is that these relations are not auto loaded when reading an object from the DB with find* functions.

要实际加载它们，您现在必须使用查询构建器并加入它们.(您可以加入多个级别.)示例:

To actually load them, you have to use query builder at the moment and join them. (You can join multiple levels.) An example:

let allServices = await this.repository.createQueryBuilder('category')
  .andWhere('category.price IS NULL')
  .innerJoinAndSelect('category.children', 'product')
  .leftJoinAndSelect('product.children', 'addon')
  .getMany();

请注意我如何使用不同的名称来引用它们(category、product 和 addon).

Please note how I used different names to reference them (category, product, and addon).

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