如何在typeORM中的@ManyToMany中保存关系 [英] How to save relation in @ManyToMany in typeORM

问题描述

有两个名为 Article 和 Classification 的实体.它们之间的关系是 @ManyToMany .

There are 2 entities named Article and Classification. And the relation of them is @ManyToMany.

这是我的问题:如何保存关系?

Here's my question: How to save the relation?

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[];
    }

我可以成功保存 Article 和 Classification .但是我不确定如何保存它们之间的关系.

I can save the Article and Classification successful. But I'm not sure how to save the relation of them.

我试图通过以下代码保存关系:

I have tried to save the relation via below code:

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;
  }

这样的发布数据结构

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

一开始就有效.

但是当我再次发布数据时，旧记录被替换了，而是创建了另一条记录.

But when I post the data again, the old record was replaced rather create another record.

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;
  }

推荐答案

如何保存关系?

让我们假设您有一系列文章，并且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.

How to save relations?

Let's assume you have an array of articles and you want to create a relation to a classification entity. You just assign the array to the property articles and save the entity; typeorm will automatically create the relation.

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

要执行此操作，必须已保存商品实体.如果希望typeorm自动保存文章实体，则可以设置 cascade 转换为 true .

For this to work, the article entities have to be saved already. If you want typeorm to automatically save the article entities, you can set cascade to true.

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

---

您的示例

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);
}

这篇关于如何在typeORM中的@ManyToMany中保存关系的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！