Graphql返回“无法读取未定义的属性'id'”，[apollo服务器，node.js]

如何解决Graphql返回“无法读取未定义的属性'id'”，[apollo服务器，node.js]

我正在尝试使用graphql和apollo服务器显示一门课程并更新课程主题。 这是我的代码：

const { ApolloServer,gql } = require('apollo-server');

var typeDefs=gql`
input CourseInput {
    id: Int
    title: String
    author: String
    description: String
    topic: String
    url: String
}
type Course {
    id: Int
    title: String
    author: String
    description:String
    topic:String
    url: String
}
type Query {
    course(id: Int!): Course
    courses(topic:String!):[Course]
    allcourses:[Course]
    hello: String

}
type Mutation {
    updateCourseTopic(id: Int !,topic: String !): Course
    createCourse(input: CourseInput): [Course]
    deleteCourse(id: Int !): [Course]
}
`;

var coursesData = [
    {
        id: 1,title: 'The Complete Node.js Developer Course',author: 'Andrew Mead,Rob Percival',description: 'Learn Node.js by building real-world applications with Node,Express,MongoDB,Mocha,and more!',topic: 'Node.js',url: 'https://codingthesmartway.com/courses/nodejs/'
    },{
        id: 2,title: 'Node.js,Express & MongoDB Dev to Deployment',author: 'Brad Traversy',description: 'Learn by example building & deploying real-world Node.js applications from absolute scratch',url: 'https://codingthesmartway.com/courses/nodejs-express-mongodb/'
    },{
        id: 3,title: 'JavaScript: Understanding The Weird Parts',author: 'Anthony Alicea',description: 'An advanced JavaScript course for everyone! Scope,closures,prototypes,this,build your own framework,and more.',topic: 'JavaScript',url: 'https://codingthesmartway.com/courses/understand-javascript/'
    }
]
var getCourses = function(args){
    console.log("delila2")
    if(args.topic){
        console.log("delila2")
        var topic=args.topic;
        return coursesData.filter(course=>
            course.topic===topic
        );

    }
    else return coursesData
    
}

var resolvers= {
Query:{
  course:getcourse,courses:getCourses,allcourses:getAllCourses,hello: ()=>"Delila"
},Mutation: {
  updateCourseTopic:updateCourseTopic,createCourse:createCourse,deleteCourse: deleteCourse,}
};

function getcourse(args){
    var id=args.id;
    return coursesData.filter(course=>{
        return course.id==id
    })[0]
 

}
function getAllCourses(){
    console.log("all courses")
    return coursesData;
}
function updateCourseTopic (id,topic){
  console.log("id je",id)
    coursesData.map(course=>{
        if(course.id===id){
            course.topic=topic;
            return course
        }
    });
    console.log("svi",coursesData);
    return coursesData.filter(course=>course.id===id)[0]
    
}
function createCourse(input){
    var id = 4;
    coursesData = [...coursesData,input.input];
    console.log("input je",input.input)
    console.log("coursesdata",coursesData)
    //coursesData[id] = input;
    return coursesData;

}
function deleteCourse(args){
    var id=args;
    coursesData.splice(id,1);
    return coursesData;

}

// The ApolloServer constructor requires two parameters: your schema
// definition and your set of resolvers.
const server = new ApolloServer({ typeDefs,resolvers });

// The `listen` method launches a web server.
server.listen().then(({ url }) => {
  console.log(`?  Server ready at ${url}`);
});

在我的本地服务器http://localhost:4000上使用graphql和这段代码，我试图获取数据以获取一门特定课程并更新课程主题。

获得单门课程：

query getSingleCourse($courseID: Int !){
  course(id:$courseID){
    title
    author
    description
    url
    topic
  }
}
{
  "courseID": 3
}

更新课程主题：

mutation updateCourse($id: Int!,$topic: String !) {
  updateCourseTopic(id:$id,topic:$topic)
  {
    title
    url
    description
    author
    topic
  }
}
{
  "id": 1,"topic": "something new"
}

getSingleCourse的问题在于

“错误”：[ { “ message”：“无法读取未定义的属性'id'，” “位置”：[ { “行”：2 “栏”：3 } ]， “路径”：[ “课程” ]， “扩展名”：{ “ code”：“ INTERNAL_SERVER_ERROR”， “例外”：{ “堆栈跟踪”： [ “ TypeError：无法读取未定义的属性'id'”， “在getcourse（/Users/admin/newProject/server4.js:116:17）”，

与updateCourse相似，ID和主题未定义

{“数据”：{ “ updateCourseTopic”：null}}

您可以看一下图片

任何人的帮助将不胜感激。

谢谢

解决方法

解析器可以选择接受四个位置参数：（父，args，上下文，信息）。

为了工作，只需指定第一个参数，如下所示：

function getcourse(_,args){
    var id=args.id;
    return coursesData.filter(course=>{
        return course.id==id
    })[0]
 

}

function updateCourseTopic (_,args){
    coursesData.map(course=>{
        if(course.id===args.id){
            course.topic=args.topic;
            return course
        }
    });
    return coursesData.filter(course=>course.id===args.id)[0]
    
}