嵌套错误：无法确定 getProducts 的 GraphQL 输出类型

Posted 2023-03-08

【中文标题】嵌套错误：无法确定 getProducts 的 GraphQL 输出类型

【英文标题】：Nest Error: Cannot determine GraphQL output type for getProducts

【发布时间】：2020-07-07 08:34:54

【问题描述】：

当我尝试从解析器返回自定义 dto 时出现此错误。 (node:28156) UnhandledPromiseRejectionWarning: Error: Cannot determine GraphQL output type for getProducts

这是我的代码的样子。

product.entity.ts

import 
  Entity,
  Column,
  PrimaryGeneratedColumn,
  BaseEntity,
  BeforeInsert,
 from 'typeorm';
import  ObjectType, Field, ID, Float, Int  from '@nestjs/graphql';

@ObjectType()
@Entity()
export class Product extends BaseEntity 
  @Field(() => ID)
  @PrimaryGeneratedColumn('uuid')
  id: string;

  @Column( default: '', select: false )
  ratingsString: string;

  @Field(() => [Int])
  ratings;

  @BeforeInsert()
  setRatingsString() 
    this.ratingsString = this.ratings.join(',');
  

product.resolver.ts

import  Resolver, Query, Args, ResolveField, Int, Parent  from '@nestjs/graphql';

import  Product  from './product.entity';
import  ProductService  from './product.service';

@Resolver(() => Product)
export class ProductResolver 
  constructor(private productService: ProductService) 

  @Query(() => GetProductDto,  name: 'products' )
  async getProducts(@Args() page: number) 
    return this.productService.getProducts(page);
  

product.service.ts

import  Injectable  from '@nestjs/common';
import  InjectRepository  from '@nestjs/typeorm';
import  Repository  from 'typeorm';

import  Product  from './product.entity';
import  GetProductDto  from './product.dto';

@Injectable()
export class ProductService 
  constructor(
    @InjectRepository(Product) private productRepo: Repository<Product>,
  ) 

  async getProducts(page: number): Promise<GetProductDto> 
    const MAX_PRODUCT_PER_PAGE = 20;
    const start = page < 1 ? 1 : page;

    const [products, productsCount] = await this.productRepo.findAndCount(
      skip: (start - 1) * MAX_PRODUCT_PER_PAGE,
      take: MAX_PRODUCT_PER_PAGE,
    );

    const productList = products.map(product => 
      product.ratings = product.ratingsString.split(',').map(Number);
      delete product.ratingsString;
      return product;
    );

    return 
      products: productList,
      total: productsCount,
    ;
  

product.dto.ts

import  Field, Int, InputType  from '@nestjs/graphql';
import  Product  from './product.entity';

@InputType()
export class GetProductDto 
  @Field(() => [Product])
  products: Product[];

  @Field(() => Int)
  total: number;

这里的期望是，当我调用产品查询时，我将收到一个包含产品和总数的对象。 Whee 产品将是我的一系列产品。我做错了什么？

【参考方案1】：

原来我只需要为 Args 提供一个参数。

  @Query(() => GetProductDto,  name: 'products' )
  async getProducts(@Args('arg_the_client_will_it_with') page: number) 
    return this.productService.getProducts(page);