Skip to main content
Version: v12.0.0

useFragment

useFragment#

import type {UserComponent_user$key} from 'UserComponent_user.graphql';
const React = require('React');
const {graphql, useFragment} = require('react-relay');
type Props = {  user: UserComponent_user$key,};
function UserComponent(props: Props) {  const data = useFragment(    graphql`      fragment UserComponent_user on User {        name        profile_picture(scale: 2) {          uri        }      }    `,    props.user,  );
  return (    <>      <h1>{data.name}</h1>      <div>        <img src={data.profile_picture?.uri} />      </div>    </>  );}

Arguments#

  • fragment: GraphQL fragment specified using a graphql template literal.
  • fragmentReference: The fragment reference is an opaque Relay object that Relay uses to read the data for the fragment from the store; more specifically, it contains information about which particular object instance the data should be read from.
    • The type of the fragment reference can be imported from the generated Flow types, from the file <fragment_name>.graphql.js, and can be used to declare the type of your Props. The name of the fragment reference type will be: <fragment_name>$key. We use our lint rule to enforce that the type of the fragment reference prop is correctly declared.

Return Value#

  • data: Object that contains data which has been read out from the Relay store; the object matches the shape of specified fragment.
    • The Flow type for data will also match this shape, and contain types derived from the GraphQL Schema. For example, the type of data above is: { name: ?string, profile_picture: ?{ uri: ?string } }.

Behavior#

  • The component is automatically subscribed to updates to the fragment data: if the data for this particular User is updated anywhere in the app (e.g. via fetching new data, or mutating existing data), the component will automatically re-render with the latest updated data.
  • The component will suspend if any data for that specific fragment is missing, and the data is currently being fetched by a parent query.

Is this page useful?