graphql - 如何在 ObjectType 字段注释中使用泛型声明 (nestjs)

Question

我需要为我的 graphql 类型创建自定义分页结果这是我的 PaginateResult 对象类型

@ObjectType()
export class PaginateResult<T> {
  @Field()
  docs: T[];

  @Field()
  totalDocs: string;

  @Field()
  totalPages: string;
}

并在解析器中调用它

  @Query((type) => PaginateResult<User>, { nullable: true })
  async getUsers(@Args({ type: () => GetAllUserArgs }) args: GetAllUserArgs) {
    const queryResolver: QueryResolver = new QueryResolver(args);
    return this.userService.getAll(queryResolver.query);
  }

和用户对象类型

@ObjectType()
export class User {
  @Field(() => ID)
  id: string;

  @Field()
  fullName: string;

  @Field()
  companyName: string;

  @Field()
  mobile: string;

  @Field({ nullable: true })
  profilePhoto?: string;

  @Field()
  isActive: boolean;
}

但这行不通

Error: Undefined type error. Make sure you are providing an explicit type for the "docs" of the "PaginateResult" class.

Answer 1

您必须定义一个 PaginateResult 类型:

import { Field, Int, ObjectType } from '@nestjs/graphql';
import { Type } from '@nestjs/common';

export function PaginateResult<T>(ItemType: Type<T>): any {
  @ObjectType({ isAbstract: true })
  abstract class PageClass {
    @Field(() => [ItemType])
    docs: T[];

    @Field(() => Int)
    totalPages: number;
  }

  return PageClass;
}

使用泛型函数工厂创建专用类型类:

import { User } from './user.model';
import { ObjectType } from '@nestjs/graphql';
import { Paginated } from 'src/types/paginated-result.type';

@ObjectType()
export class UserPage extends PaginateResult(User) {}

并在解析器中调用它

  @Query(() => UserPage)
  async getUsers(
    @Args() args: GetAllUserArgs,
  ): Promise<UserPage | HttpException> {
    return this.usersService.getAll(args);
  }