useQueryLoader

useQueryLoader

Hook used to make it easy to safely load and retain queries. It will keep a query reference stored in state, and dispose of it when the component is disposed or it is no longer accessible via state.

This hook is designed to be used with usePreloadedQuery to implement the "render-as-you-fetch" pattern. For more information, see the Fetching Queries for Render guide.

import type {AppQuery as AppQueryType} from 'AppQuery.graphql';
import type {PreloadedQuery} from 'react-relay';

const {useQueryLoader, usePreloadedQuery} = require('react-relay');

const AppQuery = graphql`
  query AppQuery($id: ID!) {
    user(id: $id) {
      name
    }
  }
`;

type Props = {
  initialQueryRef: PreloadedQuery<AppQueryType>,
};

function QueryFetcherExample(props: Props) {
  const [
    queryReference,
    loadQuery,
    disposeQuery,
  ] = useQueryLoader(
    AppQuery,
    props.initialQueryRef, /* e.g. provided by router */
  );

  if (queryReference == null) {
    return (
      <Button onClick={() => loadQuery({})}> Click to reveal the name </Button>
    );
  }

  return (
    <>
      <Button onClick={disposeQuery}>
        Click to hide the name and dispose the query.
      </Button>
      <React.Suspense fallback="Loading">
        <NameDisplay queryReference={queryReference} />
      </React.Suspense>
    </>
  );
}

function NameDisplay({ queryReference }) {
  const data = usePreloadedQuery<AppQueryType>(AppQuery, queryReference);

  return <h1>{data.user?.name}</h1>;
}

Arguments

• query: GraphQL query specified using a graphql template literal.
• initialQueryRef: [Optional] An initial PreloadedQuery to be used as the initial value of the queryReference stored in state and returned by useQueryLoader.

Flow Type Parameters

• TQuery: the type of the query

Return value

A tuple containing the following values:

• queryReference: the query reference, or null.
• loadQuery: a callback that, when executed, will load a query, which will be accessible as queryReference. If a previous query was loaded, it will dispose of it. It will throw an error if called during React's render phase.
  • Parameters
    • variables: the variables with which the query is loaded.
    • options: LoadQueryOptions. An optional options object, containing the following keys:
      • fetchPolicy: [Optional] Determines if cached data should be used, and when to send a network request based on the cached data that is currently available in the Relay store (for more details, see our Fetch Policies and Garbage Collection guides):
        • "store-or-network": (default) will reuse locally cached data and will only send a network request if any data for the query is missing. If the query is fully cached, a network request will not be made.
        • "store-and-network": will reuse locally cached data and will always send a network request, regardless of whether any data was missing from the local cache or not.
        • "network-only": will not reuse locally cached data, and will always send a network request to fetch the query, ignoring any data that might be locally cached in Relay.
      • networkCacheConfig: [Optional] Default value: {force: true}. Object containing cache config options for the network layer. Note that the network layer may contain an additional query response cache which will reuse network responses for identical queries. If you want to bypass this cache completely (which is the default behavior), pass {force: true} as the value for this option.
• disposeQuery: a callback that, when executed, will set queryReference to null and call .dispose() on it. It has type () => void. It should not be called during React's render phase.

Behavior

• The loadQuery callback will fetch data if passed a query, or data and the query if passed a preloadable concrete request. Once both the query and data are available, the data from the query will be written to the store. This differs from the behavior of preloadQuery_DEPRECATED, which would only write data to the store if the query was passed to usePreloadedQuery.
• This query reference will be retained by the Relay store, preventing the data from being garbage collected. Once .dispose() is called on the query reference, the data is liable to be garbage collected.
• The loadQuery callback will throw an error if it is called during React's render phase.

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