即使在调用查找或查找功能时，即使它们之间存在关系，实体即使它们之间有关系

Question

我正在尝试创建一个名为“作者”的实体，该实体具有已有现有实体的数组，称为书籍，返回值返回所需值，但是当我尝试查看创建的实体时，书籍的数组以null值出现。 这是我用于创建作者实体

  async create(createAuthorDto: CreateAuthorDto) {
    try {
      const found: Author[] = await this.authorRepo.find({
        where: {
          FirstName: createAuthorDto.FirstName,
          LastName: createAuthorDto.LastName,
        },
      });
      if (found.length != 0) throw Error('This author already exists');
      else {
        const booklist: Book[] = await this.createArray(createAuthorDto.Books);
        console.log('The book list is : ' + booklist);
        return await this.authorRepo.save(
          this.authorRepo.create({
            FirstName: createAuthorDto.FirstName,
            LastName: createAuthorDto.LastName,
            Books: booklist,
          }),
        );
      }
    } catch (error) {
      return error.message;
    }
  }

创建书籍实体数组的代码的代码：

  async createArray(booknames: string[]) {
    const books: Book[] = [];
    for (const bookname of booknames) {
      const book: Book | undefined = await this.bookService.findOne(bookname);
      books.push(book);
      console.log(books);
    }
    console.log('The returned value: ' + books);
    return books;
  }

作者实体的代码：

import {
  Entity,
  Column,
  PrimaryGeneratedColumn,
  ManyToMany,
  JoinTable,
} from 'typeorm';

import { Book } from '../entities/book.entity';

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

  @Column()
  FirstName: string;

  @Column()
  LastName: string;

  @ManyToMany(() => Book)
  @JoinTable()
  Books: Book[];
  //In order to create an object using the book entity I need to define constructors.
  constructor(FirstName: string, LastName: string, Books: Book[]);
  constructor(FirstName: string, LastName: string, Books: Book[], id?: number) {
    this.FirstName = FirstName || '';
    this.LastName = LastName || '';
    this.Books = Books || null;
    this.id = id || null;
  }
}

使用Postman的输出结果的某些图片：

第一张图片包含作者实体的主体，

第二个包含作者实体创建并保存之后。

第三张图片是带有空书数组的实体。

Answer 1

只需为您的作者实体添加渴望即可。
这样：

import {
  Entity,
  Column,
  PrimaryGeneratedColumn,
  ManyToMany,
  JoinTable,
} from 'typeorm';

import { Book } from '../entities/book.entity';

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

  @Column()
  FirstName: string;

  @Column()
  LastName: string;
//right here!
  @ManyToMany(() => Book,{eager:true})
  @JoinTable()
  Books: Book[];
  //In order to create an object using the book entity I need to define constructors.
  constructor(FirstName: string, LastName: string, Books: Book[]);
  constructor(FirstName: string, LastName: string, Books: Book[], id?: number) {
    this.FirstName = FirstName || '';
    this.LastName = LastName || '';
    this.Books = Books || null;
    this.id = id || null;
  }
}

如果没有急切的态度，当您调用find（）方法时，它将无法自动加入。