使用NestJS / TypeORM

Question

书店练习。可以为一个Book分配一个Genre 尝试使用DTO中提供的genreId分配一本新书。

BookRepository

    @EntityRepository(Book)
    export class BookRepository extends Repository<Book> {
      constructor(
        private genreService: GenresService,
      ) {
        super();
      }

      async createBook(createBookDto: CreateBookDto): Promise<Book> {
        const genre = await this.genreService.getOne(createBookDto.genreId);
        const newBook = this.create({
          ...createBookDto,
          genre,
        });
        return newBook.save();
      }
    }

GenreService

    @Injectable()
    export class GenresService {

      constructor(
        @InjectRepository(GenreRepository) private readonly genreRepository: GenreRepository,
      ) {}

      async getOne(id: number): Promise<Genre> {
        return this.getById(id);
      }

      private async getById(id: number): Promise<Genre> {
        const found = await this.genreRepository.findOne(id);

        if (!found) {
          throw new NotFoundException(`Genre with id ${id} not found.`);
        }

        return found;
      }
    }

BookRepository和GenreRepository由BookstoreModule一起导入，就像这样：

    imports: [
        TypeOrmModule.forFeature([
          GenreRepository,
          BookRepository,
          AuthorRepository,
        ]),
        // ...etc
    },

NestJS吐出以下错误：

[ExceptionsHandler] this.genreService.getOne is not a function +1045981ms
TypeError: this.genreService.getOne is not a function
    at BookRepository.createBook (/Users/artur/Code/Sandbox/books-nest/dist/bookstore/books/book.repository.js:21:47)
    at BooksService.createBook (/Users/artur/Code/Sandbox/books-nest/dist/bookstore/books/books.service.js:29:36)
    at BooksController.create (/Users/artur/Code/Sandbox/books-nest/dist/bookstore/books/books.controller.js:31:33)

试图注入GenreRepository into the BookRepository`

constructor(
    @InjectRepository(GenreRepository) private genreRepository: GenreRepository,
){
    super();
}

和.findOne()，错误是：

No metadata for "2" was found. +26884ms
EntityMetadataNotFound: No metadata for "2" was found.

（2是genreId的ID）

不确定我的保存方法是否正确。从BookRepository中查找流派的想法也许是错误的，应该以其他方式解决。如果可以，怎么办？

Answer 1

对我来说，createBook方法应该位于BookService内，BookService需要注入GenreService，然后您应该从{{1}内部调用genreService.getOne(createBookDto.genreId) }。
让服务处理数据流imo的业务逻辑/编排更有意义。

我建议尝试使用以下代码：

BookService

BookService

BookRepository

@Injectable()
    export class BookService {

      constructor(
        @InjectRepository(BookRepository) private readonly bookRepository: BookRepository, 
private genreService: GenreService // <= here you go, you inject the genreService into the bookService to take advantage of its methods
      ) {}

      async getOne(id: number): Promise<Genre> {
        return this.getById(id);
      }

      async createBook(createBookDto: CreateBookDto): Promise<Book> {
        const genre = await this.genreService.getOne(createBookDto.genreId);
        const newBook = this.create({
          ...createBookDto,
          genre,
        });
        return newBook.save();
      }

      private async getById(id: number): Promise<Genre> {
        const found = await this.bookRepository.findOne(id);

        if (!found) {
          throw new NotFoundException(`Book with id ${id} not found.`);
        }

        return found;
      }
    }

GenresService

    @EntityRepository(Book)
    export class BookRepository extends Repository<Book> {}

GenreRepository

    @Injectable()
    export class GenresService {

      constructor(
        @InjectRepository(GenreRepository) private readonly genreRepository: GenreRepository,
      ) {}

      async getOne(id: number): Promise<Genre> {
        return this.getById(id);
      }

      private async getById(id: number): Promise<Genre> {
        const found = await this.genreRepository.findOne(id);

        if (!found) {
          throw new NotFoundException(`Genre with id ${id} not found.`);
        }

        return found;
      }
    }

让我知道是否有帮助：）