无法解析自定义对象graphql模式

Question

我正在尝试为Apollo Server设置架构，但遇到错误。我不太确定如何提出这个问题，因此我会在必要时张贴文字/代码。

“ message”：“无法为不可为空的字段User.id返回null。”

我的resolvers / index.js看起来像这样：

import * as Mutation from "./Mutation";
import * as Query from "./Query";
import User from "./User";

const resolvers = { Mutation, Query, User };

console.log(resolvers);
export default resolvers;

将产生以下输出：

{
Mutation: {
  createListing: [Getter],
  updateListing: [Getter],
  deleteListing: [Getter],
  createUser: [Getter]
},

Query: { listings: [Getter], listing: [Getter], userLogin: [Getter] },

User: [AsyncFunction: user]
}

我的typeDefs文件看起来像这样

import { gql } from "apollo-server";

const typeDefs = gql`
	type Listing {
		description: String!
		id: ID!
		title: String!
		createdBy: User!
	}

	type User {
		id: ID!
		email: String!
	}

	type AuthData {
		id: ID!
		token: String!
		expiresIn: String!
	}

	input UserInput {
		email: String!
		password: String!
	}

	input ListingInput {
		id: ID
		title: String!
		description: String!
	}

	type Mutation {
		createUser(userInput: UserInput): User!
		createListing(listingInput: ListingInput): Listing!
		updateListing(listingInput: ListingInput): Listing!
		deleteListing(id: ID!): Boolean!
	}

	type Query {
		listings: [Listing!]!
		listing(id: ID!): Listing!
		userLogin(userInput: UserInput): AuthData!
	}
`;

export default typeDefs;

问题是我不知道如何在列表类型中获取用户数据

createdBy实际上是ID！字段，我希望graphQL为我获取用户数据。下面是我一直在尝试使用的查询。

query {
listing(id: 35) 
{
    id
	title
	createdBy {
        id
        email
    }
}
}

Graphql初学者在这里。我使用正确的方法吗？如果需要，我还可以提供git repo。我该如何重组它才能起作用？

Answer 1

如果您的解析器为必需的属性返回null，则Graphql将抛出此错误。

似乎您只为Mutation，Query和User定义了解析器，但是您想为列表创建另一个解析器，该解析器可用于解析createdBy字段。我以为它看起来像这样：

Listing.js

const Listing = {
  createdBy: (root, args, ctx) => {
    //code to fetch actual user goes here, you'd presumably have some kind of
    //id on the listing like 'creator' that refers to a user id which you could
    //access from the root like root.creator
    return {
      id: '1',
      email: '[email protected]'
    }
  }
}

export default Listing