useRefetchableFragment

useRefetchableFragment

You can use useRefetchableFragment when you want to fetch and re-render a fragment with different data:

import type {CommentBody_comment$key} from 'CommentBody_comment.graphql';

const React = require('React');

const {graphql, useRefetchableFragment} = require('react-relay');


type Props = {
  comment: CommentBody_comment$key,
};

function CommentBody(props: Props) {
  const [data, refetch] = useRefetchableFragment(
    graphql`
      fragment CommentBody_comment on Comment
      @refetchable(queryName: "CommentBodyRefetchQuery") {
        body(lang: $lang) {
          text
        }
      }
    `,
    props.comment,
  );

  return (
    <>
      <p>{data.body?.text}</p>
      <Button
        onClick={() => {
          refetch({lang: 'SPANISH'}, {fetchPolicy: 'store-or-network'})
        }}
      >
        Translate Comment
      </Button>
    </>
  );
}

module.exports = CommentBody;

Arguments

• fragment: GraphQL fragment specified using a graphql template literal. This fragment must have a @refetchable directive, otherwise using it will throw an error. 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).
  • Note that you do not need to manually specify a refetch query yourself. 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.
• 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

Tuple containing the following values

• [0] 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.
• [1] refetch: Function used to refetch the fragment with a potentially new set of variables.
  • Arguments:
    • variables: Object containing the new set of variable values to be used to fetch the @refetchable query.
      • These variables need to match GraphQL variables referenced inside the fragment.
      • However, only the variables that are intended to change for the refetch request need to be specified; any variables referenced by the fragment that are omitted from this input will fall back to using the value specified in the original parent query. So for example, to refetch the fragment with the exact same variables as it was originally fetched, you can call refetch({}).
      • Similarly, passing an id value for the $id variable is optional, unless the fragment wants to be refetched with a different id. When refetching a @refetchable fragment, Relay will already know the id of the rendered object.
    • options: [Optional] options object
      • fetchPolicy: Determines if cached data should be used, and when to send a network request based on cached data that is available. See the Fetch Policies section for full specification.
      • onComplete: Function that will be called whenever the refetch request has completed, including any incremental data payloads.
  • Return value:
    • disposable: Object containing a dispose function. Calling disposable.dispose() will cancel the refetch request.
  • Behavior:
    • Calling refetch with a new set of variables will fetch the fragment again with the newly provided variables. Note that the variables you need to provide are only the ones referenced inside the fragment. In this example, it means fetching the translated body of the currently rendered Comment, by passing a new value to the lang variable.
    • Calling refetch will re-render your component and may cause it to suspend, depending on the specified fetchPolicy and whether cached data is available or if it needs to send and wait for a network request. If refetch causes the component to suspend, you'll need to make sure that there's a Suspense boundary wrapping this component.
    • For more details on Suspense, see our Loading States with Suspense guide.

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.
  • For more details on Suspense, see our Loading States with Suspense guide.

Differences with RefetchContainer

• A refetch query no longer needs to be specified in this api, since it will be automatically generated by Relay by using a @refetchable fragment.
• Refetching no longer has a distinction between refetchVariables and renderVariables, which were previously vaguely defined concepts. Refetching will always correctly refetch and render the fragment with the variables you provide (any variables omitted in the input will fallback to using the original values from the parent query).
• Refetching will unequivocally update the component, which was not always true when calling refetch from RefetchContainer (it would depend on what you were querying for in the refetch query and if your fragment was defined on the right object type).

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