Directives

Assuming you read through the previous chapters, you should be familiar with the basics of schema definition by now.

You might have seen some funky extra bits in the schema definitions such as @paginate, @rules or @hasMany. Those are called directives and are the primary way to add functionality to your GraphQL schema.

Definition

Directives always begin with an @ symbol, followed by a unique name. They may be used at specified parts of the GraphQL schema.

This example directive @upperCase may be used on field definitions to convert the result to UPPER CASE.

directive @upperCase on FIELD_DEFINITION

type Query {
  hello: String @upperCase
}

Directives may also define arguments to enable a more flexible use, and they can be used in multiple places, depending on the specified directive location (opens new window).

directive @append(text: String) on FIELD_DEFINITION | ARGUMENT_DEFINITION

type Query {
  sayFriendly: String @append(text: ", please.")
  shout(phrase: String @append(text: "!")): String
}

Usage

Lighthouse provides a plethora of built-in schema directives that are ready to be consumed and can simply be used from within the schema.

The following example is quite dense, but it should give you an idea of what directives are capable of.

type Query {
  "Return a list of posts"
  posts(
    "Place an exact match filter (=) on the data"
    postedAt: Date @eq
    "Show only posts that match one of the given topics"
    topics: [String!] @in(key: "topic")
    "Search by title"
    title: String @like(template: "%{}%")
  ): [Post!]!
    # Require authentication
    @guard
    # Resolve as a paginated list
    @paginate
}

Explore the docs to find out more or look into the directives API reference for a complete list of all available directives.

Implementing your own directives is a great way to add reusable functionality to your schema, learn how you can implement your own directives.