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

问题描述

有 2 个实体名为 Article 和 Classification.它们的关系是@ManyToMany.

这是我的问题:如何保存关系?

我的代码如下:

 @Entity()出口类文章{@PrimaryGeneratedColumn()身份证号码;@柱子()名称:字符串；@CreateDateColumn()创建时间:日期；@UpdateDateColumn()更新时间:日期；@柱子({类型:'文本'，})内容:字符串；@柱子({默认值:0，})喜欢数量:数量；@柱子({默认值:0，})评论数量:数量；}@实体()出口类分类{@PrimaryGeneratedColumn()身份证号码;@CreateDateColumn()创建时间:日期；@UpdateDateColumn()更新时间:日期；@柱子()名称:字符串；@ManyToMany(类型=>文章)@JoinTable()文章:文章[]；}

我可以成功保存文章和分类.但我不确定如何保存它们的关系.

我尝试通过以下代码保存关系:

async create(dto: ArticleClassificationDto): Promise
但是当我再次发布数据时，旧记录被替换而不是创建另一个记录.
接下来我该怎么办?
请看下面的代码.
async create(dto: ArticleClassificationDto): Promise{this.repository.save(dto).then(article => {article.classification.forEach(item => {this.ClassificationRepository.findOne({//privous 方法是从数据库中获取所有文章并推送到这个数组中//关系:['文章']，其中:{ id: item }//现在我改变了数据结构，只包含 id 而不是 {id}}).那么(分类=> {//console.log(文章);控制台日志(分类)；//cmd 将显示 ' UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'push' of undefined' withoutous 下面行代码.但是如果我手动初始化数组，旧记录将被再次替换.//分类.文章 = [];分类.文章.推(文章)；this.ClassificationRepository.save(分类);});})})返回空；}
解决方案
如何保存关系?
假设您有一组文章，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];等待 this.classificationRepository.save(classification);
为此，必须已保存文章实体.如果想让typeorm自动保存文章实体，可以设置<代码>级联到true.
@ManyToMany(type => Article, article => article.classifications, { cascade: true })
<小时>
你的例子
async create(dto: ArticleClassificationDto): Promise{让文章 = 等待 this.repository.create(dto);article = await this.repository.save(article);const 分类 = 等待 this.classificationRepository.findByIds(article.classification, {relations: ['articles']});for (const 分类的分类) {分类.文章.推(文章)；}返回 this.classificationRepository.save(classifications);}
There are 2 entities named Article and Classification. And the relation of them is @ManyToMany.

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

My code as below:
  @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[];
    }
I can save the Article and Classification successful. But I'm not sure how to save the relation of them.

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;
  }
And the post data strcture like that
    {
        "name":"artile name",
        "content":"article content",
        "classification":[{
            "id":4
        },{
            "id":3
        }]
    }
At the beginning, it works.



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



What should I do next?

Just look below code please.
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;
  }

解决方案
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);
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 })




Your example

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);
}


                        
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