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Building Full Stack Applications with GraphQL

Nested Resolvers

Learn how to define and implement nested GraphQL resolvers.

We'll cover the following...

Defining our schema

In this lesson, we’ll add a new User type that represents information about a user who has created a post about a particular product. We’ll update our schema so that when a consumer of GraphQL API fetches data about a product, they can also fetch data about the user who posted it.

Each user object in our application will have the following fields:

  • id: The unique identifier of a user.
  • userName: User’s screen name on the website.
  • fullName: A user’s full name.

To add support for this in our schema, we need to define a new User type with these three fields:

type User {
  id: ID!,
  userName: String!,
  fullName: String!,
}

The only new feature in this type of definition is the ID type that we’ve used for the id field. This is another built-in GraphQL type that’s serialized to a string. It signifies that this is a unique identifier.

Now that we have a new User type, the second thing we need to do is specify that each object of the Product type has an author field in the schema.

type Product {
  name: String!,
  description: String!,
  url: String!,
  numberOfVotes: Int!,
  publicationAt: String!,
  # New field that we've added
  author: User!,
}

This should all be familiar by now. We specify that the author field is of a type User, which we’ve defined before, and that it should never be null.

When compared to our previous lessons in this course, the main difference is that ...