Graphql keeps returning null in graphql and express

Question

I'm trying to query data in GraphQL and express. I wrote the schema and the resolvers, but no matter what I do, it keeps returning null. I tried to re-write everything, I tried to use apollo-express, I looked everywhere but no matter what I tried it kept returning null.

const express = require("express");
const app = express();
const port = process.env.PORT || 8080;
const { graphqlHTTP } = require("express-graphql");
const { buildSchema } = require("graphql");
const cors = require("cors");

let books = [
  { name: "Name of the Wind", genre: "Fantasy", id: "1", authorId: "1" },
  { name: "The Final Empire", genre: "Fantasy", id: "2", authorId: "2" },
  { name: "The Hero of Ages", genre: "Fantasy", id: "4", authorId: "2" },
  { name: "The Long Earth", genre: "Sci-Fi", id: "3", authorId: "3" },
  { name: "The Colour of Magic", genre: "Fantasy", id: "5", authorId: "3" },
  { name: "The Light Fantastic", genre: "Fantasy", id: "6", authorId: "3" },
];

const Schema = buildSchema(`
  type Query {
    book(id: ID!): Book!
    books: [Book!]
    test: String
  }

  type Book {
    id: ID!
    name: String!
    genre: String!
    author: Author!
    
  },
  type Author {
    id: ID!
    name: String!
    age: Int!
    books: [Book]!
  }
`);

let root = {
  Query: {
    books: () => {
      return books;
    },
    book: (parent: any, args: any) => {
      Book.findById(args.id);
    },
  },
};

app.use(
  "/graphql",
  cors(),
  graphqlHTTP({
    schema: Schema, // Must be provided
    rootValue: root,
    graphiql: true,
  })
);

Here is the query:

{
  books {
    name
    id
  }
}

And here is the query response:

{
  "data": {
    "books": null
  }
}

Hope it's enough.

Answer 1

I was able to get your query to work in apollo server by excluding the below lines. Was the intention to apply findById to books?

book: (parent: any, args: any) => {
Book.findById(args.id);  
} 

See below:

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

let books = [
{ name: "Name of the Wind", genre: "Fantasy", id: "1", authorId: "1" },
{ name: "The Final Empire", genre: "Fantasy", id: "2", authorId: "2" },
{ name: "The Hero of Ages", genre: "Fantasy", id: "4", authorId: "2" },
{ name: "The Long Earth", genre: "Sci-Fi", id: "3", authorId: "3" },
{ name: "The Colour of Magic", genre: "Fantasy", id: "5", authorId: "3" },
{ name: "The Light Fantastic", genre: "Fantasy", id: "6", authorId: "3" }
];

// Construct a schema, using GraphQL schema language
const typeDefs = gql`
type Query {
book(id: ID!): Book!
books: [Book!]
test: String
}

type Book {
id: ID!
name: String!
genre: String!
author: Author!
}
type Author {
id: ID!
name: String!
age: Int!
books: [Book]!
}
`;

// Provide resolver functions for your schema fields
const resolvers = {
  Query: {
    books: () => {
    return books;
  }
}
};

const server = new ApolloServer({
typeDefs,
resolvers
});

server.listen().then(({ url }) => {
console.log(`🚀 Server ready at ${url}`);
});

Just to note: your books and Book type definition don't match (authorId vs author).