Fields

Resolver itself doesn't validate/enforce relationships between the fields

• Even the integrity of the fields' return values are enforced by the types generated from graphql-codegen

Consequently, fields can return any return value as long as defined by the resolver function

Nested Fields

You can continue to query for the nested sub-fields by referencing any of the parent fields' field values as a querying argument

Field Orders

Primitive types should be defined above the custom fields

type User {
  id: ID! # cannot be null
  pets: [Pets]
  name: String! # cannot be null
  age: Int
}

Non-null Fields (!)

! indicates that the field cannot be null

# type definitions
type User {
  id: ID! # cannot be null
  name: String! # cannot be null
  age: Int
}

Above example is requiring id and name fields to have a non-null value

• age field can be null

Handle Fetch Error on Field Manually

Resolver should explicitly handle null data on fetch

const queriedData = fetch('/some-data');

if(!queriedData || !queriedData.targetAttribute) {
  throw Error('targetAttribute does not exist');
}

const resolverFields = {
  id: queriedData.id,
  targetAttribute: queriedData.targetAttribute
};