如何在typeORM中保存@ManyToMany中的关系

Question

有两个实体名为Article和Classification。他们的关系是@ManyToMany。

这是我的问题：如何保存关系？

我的代码如下：

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

        @Column()
        name: string;

        @CreateDateColumn()
        createTime: Date;

        @UpdateDateColumn()
        updateTime: Date;

        @Column({
            type: 'text',
        })
        content: string;

        @Column({
            default: 0,
        })
        likeAmount: number;

        @Column({
            default: 0,
        })
        commentAmount: number;
    }

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

        @CreateDateColumn()
        createTime: Date;

        @UpdateDateColumn()
        updateTime: Date;

        @Column()
        name: string;

        @ManyToMany(type => Article)
        @JoinTable()
        articles: Article[];
    }

我可以成功地保存Article和Classification。但我不确定如何保存它们之间的关系。

我试图通过以下代码保存关系：

async create(dto: ArticleClassificationDto): Promise<any> {
    const article = this.repository.save(dto);
    article.then(value => {
      console.log(value);//console the object article
      value.classification.forEach(item => {
        const classification = new Classification();
        classification.id = item.id;
        classification.articles = [];
        classification.articles.push(value);
        this.classificationService.save(classification);
      })
    });
    console.log(article);
    return null;
  }

和那样的帖子数据结构

    {
        "name":"artile name",
        "content":"article content",
        "classification":[{
            "id":4
        },{
            "id":3
        }]
    }

一开始，它有效。

但是当我再次发布数据时，旧记录被替换而不是创建另一条记录。

接下来我该怎么办？

请看下面的代码。

async create(dto: ArticleClassificationDto): Promise<any> {
    this.repository.save(dto).then(article => {
      article.classification.forEach(item => {
        this.ClassificationRepository.findOne(
          {
            // the privous method is get all the articles from databse and push into this array
            // relations: ['articles'],
            where: { id: item }// now I change the data strcture, just contains id instead of {id}
          }
        ).then(classification => {
          // console.log(article);
          console.log(classification);
          // cmd will show ' UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'push' of undefined' withous below line code. But if I init the array manually,the old record will be replaced again.
          // classification.articles = [];
          classification.articles.push(article);
          this.ClassificationRepository.save(classification);
        });
      })
    })
    return null;
  }

Answer 1

如何保存关系？

假设您有一系列文章，并且您想要创建与分类实体的关系。您只需将数组分配给属性articles并保存实体; typeorm将自动创建关系。

classification.articles = [article1, article2];
await this.classificationRepository.save(classification);

为此，必须保存文章实体。如果希望typeorm自动保存文章实体，可以将cascade设置为true。

@ManyToMany(type => Article, article => article.classifications, { cascade: true })

---

你的榜样

async create(dto: ArticleClassificationDto): Promise<any> {
  let article = await this.repository.create(dto);
  article = await this.repository.save(article);
  const classifications = await this.classificationRepository.findByIds(article.classification, {relations: ['articles']});
  for (const classification of classifications) {
    classification.articles.push(article);
  }
  return this.classificationRepository.save(classifications);
}