嵌套错误：无法确定 getProducts 的 GraphQL 输出类型答案

【问题标题】：Nest Error: Cannot determine GraphQL output type for getProducts嵌套错误：无法确定 getProducts 的 GraphQL 输出类型
【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？

【问题讨论】：

标签： graphql nestjs typeorm

【解决方案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);
  }

【讨论】：