How to create a nested resolver in apollo graphql server

Question

Given the following apollo server graphql schema I wanted to break these down into separate modules so I don't want the author query under the root Query schema.. and want it separated. So i added another layer called authorQueries before adding it to the Root Query

type Author {     id: Int,     firstName: String,     lastName: String }   type authorQueries {     author(firstName: String, lastName: String): Author }  type Query {     authorQueries: authorQueries }  schema {     query: Query } 

I tried the following.. you can see that authorQueries was added as another layer before the author function is specified.

Query: {     authorQueries :{         author (root, args) {             return {}        }     } } 

When querying in Graphiql, I also added that extra layer..

{     authorQueries {         author(firstName: "Stephen") {             id         }     } } 

I get the following error.

"message": "Resolve function for \"Query.authorQueries\" returned undefined",

Answer 1

To create a "nested" resolver, simply define the resolver on the return type of the parent field. In this case, your authorQueries field returns the type authorQueries, so you can put your resolver there:

{   Query: { authorQueries: () => ({}) },   authorQueries: {     author(root, args) {       return "Hello, world!";     }   } } 

So in the technical sense, there is no such thing as a nested resolver - every object type has a flat list of fields, and those fields have return types. The nesting of the GraphQL query is what makes the result nested.

Answer 2

Apollo Official related docs (Great example inside):

Resolver chains

https://www.apollographql.com/docs/apollo-server/data/resolvers/#resolver-chains

/* code from: https://www.apollographql.com/docs/apollo-server/data/resolvers/#resolver-chains */  const { ApolloServer, gql } = require('apollo-server');  const libraries = [   {     branch: 'downtown'   },   {     branch: 'riverside'   }, ];  // The branch field of a book indicates which library has it in stock const books = [   {     title: 'The Awakening',     author: 'Kate Chopin',     branch: 'riverside'   },   {     title: 'City of Glass',     author: 'Paul Auster',     branch: 'downtown'   }, ];  // Schema definition const typeDefs = gql`  # A library has a branch and books   type Library {     branch: String!     books: [Book!]   }    # A book has a title and author   type Book {     title: String!     author: Author!   }    # An author has a name   type Author {     name: String!   }    # Queries can fetch a list of libraries   type Query {     libraries: [Library]   } `;  // Resolver map const resolvers = {   Query: {     libraries() {        // Return our hardcoded array of libraries       return libraries;     }   },   Library: {     books(parent) {        // Filter the hardcoded array of books to only include       // books that are located at the correct branch       return books.filter(book => book.branch === parent.branch);     }   },   Book: {      // The parent resolver (Library.books) returns an object with the     // author's name in the "author" field. Return a JSON object containing     // the name, because this field expects an object.     author(parent) {       return {         name: parent.author       };     }   }    // Because Book.author returns an object with a "name" field,   // Apollo Server's default resolver for Author.name will work.   // We don't need to define one. };  // Pass schema definition and resolvers to the // ApolloServer constructor const server = new ApolloServer({ typeDefs, resolvers });  // Launch the server server.listen().then(({ url }) => {   console.log(`🚀  Server ready at ${url}`); });