Node.js NodeJs中的GraphQl-对象类型的解析器

我刚刚开始在NodeJs中使用GraphQl。我理解类型的解析器在下面的示例中的编码

但我无法找出关系类型的解析器的位置。例如，下面的类型Book有一个属性author，如果查询该属性，它应该返回author类型。我应该将解析程序放在哪里来解析本书的作者

// Construct a schema, using GraphQL schema language
var schema = buildSchema(`  
  type Book {
      id: ID!
      name: String!
      genre: String!
      author: Author
  }
  type Author {
      id: ID!
      name: String!
      age: String!
  }

  type Query {
      books: [Book]
      authors: [Author]
      book(id: ID): Book
      author(id: ID): Author
  }
`);

const root = {
    books: () => {
        return Book.find({});
    },
    authors: () => {
        return Author.find({});
    },
    book:({id}) => {
        return Book.findById(id);
    },
    author:({id}) => {
        return Author.findById(id);
    }
}

const app = express()
app.listen(5000, () =>{
   console.log('listening for request');
})

app.use('/graphql', graphqlHTTP({
    schema: schema,
    rootValue: root,
    graphiql: true
}))

---

您需要为图书类型定义特定的解析器。我建议您通过这种方式获取

makeExecutableSchema

，您可以轻松构建所需的关系解析器。我已复制并更改了您的解决方案，以实现预期结果

const graphqlHTTP = require("express-graphql")
const express = require("express");
const { makeExecutableSchema } = require("graphql-tools")

const typeDefs = `  
  type Book {
      id: ID!
      name: String!
      genre: String!
      author: Author
  }
  type Author {
      id: ID!
      name: String!
      age: String!
  }

  type Query {
      books: [Book]
      authors: [Author]
      book(id: ID): Book
      author(id: ID): Author
  }
`;

const resolvers = {
    Book: {
        author: (rootValue, args) => {
            // rootValue is a resolved Book type.

            return {
                id: "id",
                name: "dan",
                age: "20"
            }
        }
    },
    Query: {
        books: (rootValue, args) => {
            return [{ id: "id", name: "name", genre: "shshjs" }];
        },
        authors: (rootValue, args) => {
            return Author.find({});
        },
        book: (rootValue, { id }) => {
            return Book.findById(id);
        },
        author: (rootValue, { id }) => {
            return Author.findById(id);
        }
    }
}

const app = express();

app.listen(5000, () => {
    console.log('listening for request');
})

app.use('/graphql', graphqlHTTP({
    schema: makeExecutableSchema({ typeDefs, resolvers }),
    graphiql: true
}))

---

我相信是这样。在将graphqlHTTP设置为express的中间件时，我使用这个rootValue:root。我正在扩展这些官方文件目前非常缺乏的例子。“你真是太棒了！”丹尼尔里登说。你给了我我想要的东西。这澄清了我的许多问题。谢谢