"字段 \"createUser\" 不能有选择，因为类型 \"[String]\" 没有子字段。"答案

【问题标题】："Field \"createUser\" must not have a selection since type \"[String]\" has no subfields.""字段 \"createUser\" 不能有选择，因为类型 \"[String]\" 没有子字段。"
【发布时间】：2022-01-05 00:10:51
【问题描述】：

我是新手，请耐心等待。我正在尝试这种突变

mutation{
  createUser(userInput:{email:"test21m@g.com", password:"1223"}){
    _id
    email
  }
}

但我收到此错误：

"message": "字段 "createUser" 不能有选择，因为类型 "[String]" 没有子字段。",

文件结构如下 schema.js

const {buildSchema} = require('graphql')

module.exports = buildSchema(`
        type Booking{
        _id: ID!
        event:Event!
        user: User!
        createdAt: String!
        updatedAt: String!
    }

    type Event {
        _id:ID!
        title:String!
        description:String!
        price:Float!
        date:String!
        creator:String!
    }

    type User{
        _id: ID!
        email: String!
        password: String
        createdEvents:[Event!]
    }

    type AuthData{
        userId: ID!
        token: String!
        tokenExpiration: Int!
    }

    input EventInput {
        title:String!
        description:String!
        price:Float!
        date:String!
    }

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

    type RootQuery {
        events:[Event!]!
        bookings: [Booking!]!
        login(email: String!, password: String!): AuthData!
    }

    type RootMutation{
        createEvent(eventInput : EventInput):[String]
        createUser(userInput: UserInput):[String]
        bookEvent(eventId: ID!): Booking!
        cancelBooking(bookingId: ID!): Event!
    }

    schema {
        query   :   RootQuery
        mutation:   RootMutation
    }
`)

auth-resover.js

const bcrypt = require('bcryptjs')
const User = require('../../models/user')
const jwt = require('jsonwebtoken')

module.exports = {   
    // Create User Resolver __________________________________________________

    createUser: async args =>{
        try{
            const existingUser = await User.findOne({email:args.userInput.email})
            if(existingUser) throw new Error('User exists already.')

            const hashedPassword =  await bcrypt.hash(args.userInput.password, 12)

            const user = new User({
                email: args.userInput.email,
                password: args.userInput.password
            })

            const result = await user.save()

            return {...result._doc, password:null,  _id: result.id}    

        }catch(err) { throw err }
    },  
// end of User Resolver __________________________________________________


    //this name has to match the name in "type RootQuery" schema-index.js
    login: async({email, password}) => {
        const user = await User.findOne({email:email})
        if(!user) throw new Error('Invalid Cridentials: user not found')

        const isEqual = await bcrypt.compare(password, user.password)
        if(!isEqual) throw new Error('Invalid Cridentials: password is incorrect')

        const token = await jwt.sign(
                                {userId: user.id, email: user.email},
                                'superLongerSuperSecretKey',
                                {expriresIn:'1h'}) 
        return { 
                userId: user.id, 
                token: token, 
                tokenExpiration: 1}
    }
}

【问题讨论】：

标签： javascript graphql schema mutation resolver

【解决方案1】：

GraphQL 对你大喊大叫，因为突变的 [String] 返回类型没有子字段。只有 Object Types（如您的 User 类型）有子字段。

您的架构说 createUser 突变返回一个字符串列表。如果你想返回创建用户的突变，更新架构（和解析器）以返回User：

createUser(userInput: UserInput): User

【讨论】：

谢谢，成功了！