GraphQL Directives

Relay uses directives to add additional information to GraphQL documents, which are used by the Relay compiler to generate the appropriate runtime artifacts. These directives only appear in your application code and are removed from requests sent to your GraphQL server.

**Note:** The Relay compiler will maintain any directives supported by your server (such as `@include` or `@skip`) so they remain part of the request to the GraphQL server and won't alter generated runtime artifacts.

@arguments

@arguments is a directive used to pass arguments to a fragment that was defined using @argumentDefinitions. For example:

query TodoListQuery($userID: ID) {
  ...TodoList_list @arguments(count: $count, userID: $userID) # Pass arguments here
}

@argumentDefinitions

@argumentDefinitions is a directive used to specify arguments taken by a fragment. For example:

fragment TodoList_list on TodoList
@argumentDefinitions(
  count: {type: "Int", defaultValue: 10} # Optional argument
  userID: {type: "ID"} # Required argument
) {
  title
  todoItems(userID: $userID, first: $count) {
    # Use fragment arguments here as variables
    ...TodoItem_item
  }
}

Provided Variables

A provided variable is a special fragment variable whose value is supplied by a specified provider function at runtime. This simplifies supplying device attributes, user experiment flags, and other runtime constants to graphql fragments.

To add a provided variable:

• add an argument with provider: "[JSModule].relayprovider" to @argumentDefinitions
• ensure that [JSModule].relayprovider.js exists and exports a get() function
  • get should return the same value on every call for a given run.

fragment TodoItem_item on TodoList
@argumentDefinitions(
  include_timestamp: {
    type: "Boolean!"
    provider: "Todo_ShouldIncludeTimestamp.relayprovider"
  }
) {
  timestamp @include(if: $include_timestamp)
  text
}

// Todo_ShouldIncludeTimestamp.relayprovider.js
export default {
  get(): boolean {
    // must always return true or false for a given run
    return check('todo_should_include_timestamp');
  },
};

Notes:

• Even though fragments declare provided variables in argumentDefinitions, their parent cannot pass provided variables through @arguments.
• An argument definition cannot specify both a provider and a defaultValue.
• Unstable / subject to change
  • Relay transforms provided variables to operation root variables and renames them to __relay_internal__pv__[JsModule].
    • Only relevant if you are debugging a query that uses provided variables.

@catch

@catch is a directive you can add to fields in your Relay queries to declare how field-level exceptions are handled in runtime.

See also the @catch guide.

@connection(key: String!, filters: [String])

With usePaginationFragment, Relay expects connection fields to be annotated with a @connection directive. For more detailed information and an example, check out the docs on usePaginationFragment.

@refetchable(queryName: String!, directives: [String], preferFetchable: Boolean)

With useRefetchableFragment and usePaginationFragment, Relay expects a @refetchable directive. The @refetchable directive can only be added to fragments that are "refetchable", that is, on fragments that are declared on Viewer or Query types, or on a type that implements Node (i.e. a type that has an id). The @refetchable directive will autogenerate a query with the specified queryName. This will also generate Flow types for the query, available to import from the generated file: <queryName>.graphql.js. For more detailed information and examples, check out the docs on useRefetchableFragment or usePaginationFragment.

Optionally, you can pass in a list of directives to add to the autogenerated query. For example, this can be used to add the @relay_test_operation directive for testing:

[Optional] preferFetchable: Boolean

This argument tells the Relay compiler to prefer generating fetch_MyType(): MyType queries for types that implement the Node interface. This is useful for schemas that have adopted the @strong and @fetchable server annotations for types. You can directly fetch concrete objects without needing to refine Node interface to a specific type.

graphql`
  fragment FriendsListComponent_user on User
  @refetchable(
    queryName: "FriendsListFetchQuery"
    directives: ["@relay_test_operation"]
  ) {
    ...
  }
`;

@relay(plural: Boolean)

When defining a fragment for use with a Fragment container, you can use the @relay(plural: true) directive to indicate that container expects the prop for that fragment to be a list of items instead of a single item. A query or parent that spreads a @relay(plural: true) fragment should do so within a plural field (ie a field backed by a GraphQL list. For example:

// Plural fragment definition
graphql`
  fragment TodoItems_items on TodoItem @relay(plural: true) {
    id
    text
  }
`;

// Plural fragment usage: note the parent type is a list of items (`TodoItem[]`)
fragment TodoApp_app on App {
  items {
    // parent type is a list here
    ...TodoItem_items
  }
}

@required

@required is a directive you can add to fields in your Relay queries to declare how null values should be handled at runtime.

See also the @required guide.

@throwOnFieldError

@throwOnFieldError is a directive you can add to your Relay queries and fragments to have Relay throw if any field errors are encountered when reading the query or fragment. Adding the directive will allow Relay to generate non-null types for any fields marked as @semanticNonNull in the schema.

See also the @throwOnFieldError guide.

Read more about Relay's experimental support for Semantic Nullability.

@semanticNonNull

The @semanticNonNull directive can be added to fields in your schema to indicate that the field is non-nullable in the semantic sense, but that the client should still be prepared to handle errors.

Read more about Relay's experimental support for Semantic Nullability.

@alias

@alias is a directive that allows you to give a fragment spread or inline fragment an alias, similar to a field alias. This is useful when you want to conditionally include a fragment and check if it was fetched, or otherwise group data together.

For fragment spreads, the alias will default to the fragment name. For inline fragments, the alias will default to the type name. If you wish to supply your own name, or you have an inline fragment without any type condition, you can specify the alias using the as argument.

fragment MyFragment on User {
  ... on User @alias(as: "myGreatAlias") {
    name
  }
}

See also the @alias guide.

@inline

The hooks APIs that Relay exposes allow you to read data from the store only during the render phase. In order to read data from outside of the render phase (or from outside of React), Relay exposes the @inline directive. The data from a fragment annotated with @inline can be read using readInlineData.

In the example below, the function processItemData is called from a React component. It requires an item object with a specific set of fields. All React components that use this function should spread the processItemData_item fragment to ensure all of the correct item data is loaded for this function.

import {graphql, readInlineData} from 'react-relay';

// non-React function called from React
function processItemData(itemRef) {
  const item = readInlineData(
    graphql`
      fragment processItemData_item on Item @inline {
        title
        price
        creator {
          name
        }
      }
    `,
    itemRef,
  );
  sendToThirdPartyApi({
    title: item.title,
    price: item.price,
    creatorName: item.creator.name,
  });
}

export default function MyComponent({item}) {
  function handleClick() {
    processItemData(item);
  }

  const data = useFragment(
    graphql`
      fragment MyComponent_item on Item {
        ...processItemData_item
        title
      }
    `,
    item,
  );

  return <button onClick={handleClick}>Process {item.title}</button>;
}

@relay(mask: Boolean)

It is not recommended to use @relay(mask: false). Please instead consider using the @inline fragment.

@relay(mask: false) can be used to prevent data masking; when including a fragment and annotating it with @relay(mask: false), its data will be available directly to the parent instead of being masked for a different container.

Applied to a fragment definition, @relay(mask: false) changes the generated Flow types to be better usable when the fragment is included with the same directive. The Flow types will no longer be exact objects and no longer contain internal marker fields.

This may be helpful to reduce redundant fragments when dealing with nested or recursive data within a single Component.

Keep in mind that it is typically considered an anti-pattern to create a single fragment shared across many containers. Abusing this directive could result in over-fetching in your application.

In the example below, the user prop will include the data for id and name fields wherever ...Component_internUser is included, instead of Relay's normal behavior to mask those fields:

graphql`
  fragment Component_internUser on InternUser @relay(mask: false) {
    id
    name
  }
`;

@waterfall

With Relay Resolvers it's possible to create client-defined edges in the graph which point to server types. When reading these edge fields, Relay is forced to lazily fetch the server data for the edge. This will force Relay to make a second request to the server to fetch the data for the edge.

To highlight this tradeoff both in the editor and during code review, the Relay compiler expects all reads of these fields to be annotated as @waterfall.

fragment EditPost on DraftPost {
  author @waterfall {
    name
  }
}

See the Return Type portion of the Relay Resolvers guide for more information.

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