Object Types and Relationships

Build the mental model

A field on a GraphQL object type can be another object type rather than a scalar — this models a relational database's foreign-key relationships directly in the schema. When executing a query, GraphQL calls a separate resolver function for each field; resolving `Tutorial.author` reads `authorId` off the parent tutorial object and fetches the author data.

Connect it to a real scenario

Declare an `Author` type with `id`, `name`, and `tutorials: [Tutorial!]!`, and add an `author: Author!` field on `Tutorial`. A single query now fetches tutorial fields and the author's name in one round trip — where the REST version needed two endpoints.

• Object fields can reference another object type, modeling relationships in the schema
• Every field has its own resolver function
• Nested relationships fetch related data in one round trip

Try the working example

type Author {
  id: ID!
  name: String!
  tutorials: [Tutorial!]!
}

type Tutorial {
  id: ID!
  title: String!
  author: Author!
}

type Query {
  tutorial(id: ID!): Tutorial
}

You can write nested object types and model a relationship field in the schema.

GraphQL — Schemas and Types — GraphQL