Hooks (experimental)

Apollo Client experimental react hooks API reference

`useBackgroundQuery` and `useReadQuery`

Installation

⚠️ The useBackgroundQuery and useReadQuery hooks are currently at the beta stage in Apollo Client. If you have feedback on them, please let us know via GitHub issues.

Apollo Client has beta support for the useBackgroundQuery and useReadQuery hooks, which work with React's Suspense feature. You can install it via npm install @apollo/client@beta.

Using `useBackgroundQuery` and `useReadQuery`

Create and provide a SuspenseCache instance to your ApolloProvider.

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import { SuspenseCache } from '@apollo/client';
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const suspenseCache = new SuspenseCache();
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<ApolloProvider suspenseCache={suspenseCache} />;

useBackgroundQuery allows a user to initiate a query outside of the component that will read and render the data with useReadQuery, which triggers the nearest Suspense boundary while the query is pending. This means a query can be initiated higher up in the React render tree and your application can begin requesting data before the component that has a dependency on that data begins rendering.

Ensure the component tree that uses useReadQuery is wrapped with React's Suspense component. Note that the useReadQuery hook returns only data, error and networkStatus (though networkStatus should rarely be needed). Since Suspense provides the tools to manage our application's loading states, useReadQuery does not return a loading boolean.

See the API references for useBackgroundQuery and useReadQuery for supported options.

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import { Suspense } from 'react';
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import {
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  ApolloClient,
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  InMemoryCache,
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  SuspenseCache,
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  useBackgroundQuery,
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  useReadQuery,
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} from '@apollo/client';
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const query = gql`
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  foo {
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    bar
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  }
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`;
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const suspenseCache = new SuspenseCache();
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const client = new ApolloClient({
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  uri: "http://localhost:4000/graphql",
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  cache: new InMemoryCache()
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});
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function SuspenseFallback() {
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  return <div>Loading...</div>;
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}
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function Child({ queryRef }) {
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  const { data } = useReadQuery(queryRef);
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  return <div>{data.foo.bar}</div>;
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}
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function Parent() {
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  const [queryRef] = useBackgroundQuery(query);
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  return (
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    <Suspense fallback={<SuspenseFallback />}>
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      <Child queryRef={queryRef} />
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    </Suspense>
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  );
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}
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function App() {
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  return (
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    <ApolloProvider client={client} suspenseCache={suspenseCache}>
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      <ErrorBoundary fallback={<div>Error</div>}>
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        <Parent />
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      </ErrorBoundary>
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    </ApolloProvider>
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  );
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}

`useBackgroundQuery` API

Function Signature

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function useBackgroundQuery<
2
  TData = any,
3
  TVariables extends OperationVariables = OperationVariables
4
>(
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  query: query: DocumentNode | TypedDocumentNode<TData, TVariables>,
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  options: Omit<
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    SuspenseQueryHookOptions<TData, TVariables>,
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    'returnPartialData' | 'refetchWritePolicy'
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  >,
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): UseBackgroundQueryResult<TData> {}

Params

`query`

Param	Type	Description
`query`	DocumentNode	A GraphQL query document parsed into an AST by `gql`.

`options`

Name / Type	Description
Operation options
`variables` `{ [key: string]: any }`	An object containing all of the GraphQL variables your query requires to execute. Each key in the object corresponds to a variable name, and that key's value corresponds to the variable value.
`errorPolicy` `ErrorPolicy`	Specifies how the query handles a response that returns both GraphQL errors and partial results. For details, see GraphQL error policies. The default value is `none`, which causes the `useReadQuery` hook to throw the error.
Networking options
`context` `Record<string, any>`	If you're using Apollo Link, this object is the initial value of the `context` object that's passed along your link chain.
`canonizeResults` `Boolean`	If `true`, result objects read from the cache will be canonized, which means deeply-equal objects will also be `===` (literally the same object), allowing much more efficient comparison of past/present results. The default value is `false`.
`client` `ApolloClient`	The instance of `ApolloClient` to use to execute the query. By default, the instance that's passed down via context is used, but you can provide a different instance here.
Caching options
`fetchPolicy` `SuspenseQueryHookFetchPolicy`	Specifies how the query interacts with the Apollo Client cache during execution (for example, whether it checks the cache for results before sending a request to the server). For details, see Setting a fetch policy. This hook only supports the `cache-first`, `network-only`, `no-cache`, and `cache-and-network` fetch policies. The default value is `cache-first`.

Result

Name / Type	Description
Query reference
`queryRef` `QueryReference<TData>`	In order to link a query initiated by a specific `useBackgroundQuery` call to the place its data is consumed—which can be uniquely identified not only by the query and variables passed, but also the optional `queryKey` supplied by the user—the hook returns a `queryRef` that can later be read by `useReadQuery`.
Helper functions
`refetch` `(variables?: Partial<TVariables>) => Promise<ApolloQueryResult>`	A function that enables you to re-execute the query, optionally passing in new `variables`. To guarantee that the refetch performs a network request, its `fetchPolicy` is set to `network-only` (unless the original query's `fetchPolicy` is `no-cache` or `cache-and-network`, which also guarantee a network request). Calling this function will cause the component to re-suspend, unless the call site is wrapped in `startTransition`.
`fetchMore` `({ query?: DocumentNode, variables?: TVariables, updateQuery: Function}) => Promise<ApolloQueryResult>`	A function that helps you fetch the next set of results for a paginated list field. Calling this function will cause the component to re-suspend, unless the call site is wrapped in `startTransition`.

`useReadQuery` API

Function Signature

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function useReadQuery<TData>(
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  queryRef: QueryReference<TData>
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): {
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  data: TData;
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  networkStatus: NetworkStatus;
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  error: ApolloError | undefined;
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} {}

Params

`queryRef`

Param	Type	Description
`queryRef`	QueryReference	The `queryRef` that was generated via `useBackgroundQuery`.

Result

Name / Type	Description
Operation result
`data` `TData`	An object containing the result of your GraphQL query after it completes. This value might be `undefined` if a query results in one or more errors (depending on the query's `errorPolicy`).
`error` `ApolloError`	If the query produces one or more errors, this object contains either an array of `graphQLErrors` or a single `networkError`. Otherwise, this value is `undefined`. This property can be ignored when using the default `errorPolicy` or an `errorPolicy` of `none`. The hook will throw the error instead of setting this property.
`networkStatus` `NetworkStatus`	A number indicating the current network state of the query's associated request. See possible values.

`useFragment`

Installation

⚠️ The useFragment hook is currently at the beta stage in Apollo Client. If you have feedback on it, please let us know via GitHub issues.

Beginning with version 3.7.0, Apollo Client has preview support for the useFragment hook, which represents a lightweight live binding into the Apollo Client Cache. This hook returns an always-up-to-date view of whatever data the cache currently contains for a given fragment. useFragment never triggers network requests of its own.

Note: this hook is named useFragment_experimental in 3.7.x and 3.8.0-alpha.x releases. In 3.8.0-beta.0 and greater it no longer has an _experimental suffix.

useFragment enables Apollo Client to broadcast very specific fragment results to individual components. Note that the useQuery hook remains the primary hook responsible for querying and populating data in the cache (see the API reference). As a result, the component reading the fragment data via useFragment is still subscribed to all changes in the query data, but receives updates only when that fragment's specific data change.

Using `useFragment`

A GraphQL fragment defines a subset of fields on a GraphQL type that can be used to specify component-level data dependencies or allow re-use between multiple queries and mutations. See the API reference.

Given the following fragment definition:

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const ItemFragment = gql`
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  fragment ItemFragment on Item {
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    text
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  }
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`;

We can first use the useQuery hook to retrieve a list of items with ids.

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const listQuery = gql`
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  query {
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    list {
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      id
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    }
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  }
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`;
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function List() {
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  const { loading, data } = useQuery(listQuery);
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  return (
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    <ol>
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      {data?.list.map(item => (
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        <Item key={item.id} id={item.id}/>
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      ))}
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    </ol>
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  );
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}

We can then use useFragment from within the <Item> component to create a live binding for each item by providing the fragment document, fragmentName and object reference via from.

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function Item(props: { id: number }) {
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  const { complete, data } = useFragment({
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    fragment: ItemFragment,
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    fragmentName: "ItemFragment",
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    from: {
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      __typename: "Item",
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      id: props.id,
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    },
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  });
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  return <li>{complete ? data!.text : "incomplete"}</li>;
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}

useFragment can be used in combination with the @nonreactive directive in cases where list items should react to individual cache updates without rerendering the entire list. For more information, see the @nonreactive docs.

`useFragment` API

Supported options and result fields for the useFragment hook are listed below.

Most calls to useFragment can omit the majority of these options, but it's useful to know they exist.

Options

The useFragment hook accepts the following options:

Name / Type	Description
Operation options
`from` `string \| StoreObject \| Reference`	Required. An object containing a `__typename` and primary key fields (such as `id`) identifying the entity object from which the fragment will be retrieved, or a `{ __ref: "..." }` reference, or a `string` ID (uncommon).
`fragment` `DocumentNode`	Required. A GraphQL fragment document parsed into an AST with the `gql` template literal.
`fragmentName` `string`	The name of the fragment defined in the `fragment` document to use in the call. Required if the `fragment` document includes more than one fragment, optional otherwise.
`optimistic` `boolean`	If `true`, `readFragment` returns optimistic results. The default value is `true`.
`variables` `{ [key: string]: any }`	An object containing all of the GraphQL variables your fragment requires. Each key in the object corresponds to a variable name, and that key's value corresponds to the variable value.
`returnPartialData` `boolean`	If `true`, the query can return partial results from the cache if the cache doesn't contain results for all queried fields. The default value is `true`.
`canonizeResults` `boolean`	If `true`, result objects read from the cache will be canonized, which means deeply-equal objects will also be `===` (literally the same object), allowing much more efficient comparison of past/present results. The default value is `false`.

Result

Name / Type	Description
Operation result
`data` `TData`	An object containing the data for a given GraphQL fragment. This value might be `undefined` if a query results in one or more errors (depending on the query's `errorPolicy`).
`complete` `boolean`	A boolean indicating whether the data returned for the fragment is complete. When `false`, the `missing` field should explain which fields were responsible for the incompleteness.
`missing` `MissingTree`	A tree of all `MissingFieldError` messages reported during fragment reading, where the branches of the tree indicate the paths of the errors within the query result.

`useSuspenseQuery`

Installation

⚠️ The useSuspenseQuery hook is currently at the beta stage in Apollo Client. If you have feedback on it, please let us know via GitHub issues.

Apollo Client has beta support for the useSuspenseQuery hook, which works with React's Suspense feature. You can install it via npm install @apollo/client@beta.

Using `useSuspenseQuery`

Create and provide a SuspenseCache instance to your ApolloProvider.

1
import { SuspenseCache } from '@apollo/client';
2

3
const suspenseCache = new SuspenseCache();
4

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<ApolloProvider suspenseCache={suspenseCache} />;

Write queries using useSuspenseQuery. Ensure the component is wrapped with React's Suspense component. Note that the hook returns only data and error: since Suspense provides the tools to manage our application's loading states, useSuspenseQuery does not return a loading boolean.

See the API reference for supported options.

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import { Suspense } from 'react';
2
import { useSuspenseQuery } from '@apollo/client';
3

4
const listQuery = gql`
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  query {
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    list {
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      id
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    }
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  }
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`;
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function App() {
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  return (
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    <Suspense fallback={<Spinner />}>
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      <List />
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    </Suspense>
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  );
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}
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function List() {
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  const { data } = useSuspenseQuery(listQuery);
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  return (
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    <ol>
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      {data.list.map(item => <Item key={item.id} id={item.id}/>)}
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    </ol>
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  );
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}

`useSuspenseQuery` API

Function Signature

1
function useSuspenseQuery<
2
  TData = any,
3
  TVariables extends OperationVariables = OperationVariables
4
>(
5
  query: DocumentNode,
6
  options?: SuspenseQueryHookOptions<TData, TVariables>,
7
): UseSuspenseQueryResult<TData, TVariables> {}

Params

`query`

Param	Type	Description
`query`	DocumentNode	A GraphQL query document parsed into an AST by `gql`.

`options`

Name / Type	Description
Operation options
`variables` `{ [key: string]: any }`	An object containing all of the GraphQL variables your query requires to execute. Each key in the object corresponds to a variable name, and that key's value corresponds to the variable value.
`errorPolicy` `ErrorPolicy`	Specifies how the query handles a response that returns both GraphQL errors and partial results. For details, see GraphQL error policies. The default value is `none`, which causes the hook to throw the error.
Networking options
`context` `Record<string, any>`	If you're using Apollo Link, this object is the initial value of the `context` object that's passed along your link chain.
`canonizeResults` `Boolean`	If `true`, result objects read from the cache will be canonized, which means deeply-equal objects will also be `===` (literally the same object), allowing much more efficient comparison of past/present results. The default value is `false`.
`client` `ApolloClient`	The instance of `ApolloClient` to use to execute the query. By default, the instance that's passed down via context is used, but you can provide a different instance here.
Caching options
`fetchPolicy` `SuspenseQueryHookFetchPolicy`	Specifies how the query interacts with the Apollo Client cache during execution (for example, whether it checks the cache for results before sending a request to the server). For details, see Setting a fetch policy. This hook only supports the `cache-first`, `network-only`, `no-cache`, and `cache-and-network` fetch policies. The default value is `cache-first`.
`returnPartialData` `boolean`	If `true`, the query can return partial results from the cache if the cache doesn't contain results for all queried fields. The default value is `false`.
`refetchWritePolicy` `"merge" \| "overwrite"`	Watched queries must opt into overwriting existing data on refetch, by passing `refetchWritePolicy: "overwrite"` in their `WatchQueryOptions`. The default value is `"overwrite"`.

Result

Name / Type	Description
Operation result
`data` `TData`	An object containing the result of your GraphQL query after it completes. This value might be `undefined` if a query results in one or more errors (depending on the query's `errorPolicy`).
`error` `ApolloError`	If the query produces one or more errors, this object contains either an array of `graphQLErrors` or a single `networkError`. Otherwise, this value is `undefined`. This property can be ignored when using the default `errorPolicy` or an `errorPolicy` of `none`. The hook will throw the error instead of setting this property.
`networkStatus` `NetworkStatus`	A number indicating the current network state of the query's associated request. See possible values.
Client
`client` `ApolloClient`	The instance of Apollo Client that executed the query. Can be useful for manually executing followup queries or writing data to the cache.
Helper functions
`refetch` `(variables?: Partial<TVariables>) => Promise<ApolloQueryResult>`	A function that enables you to re-execute the query, optionally passing in new `variables`. To guarantee that the refetch performs a network request, its `fetchPolicy` is set to `network-only` (unless the original query's `fetchPolicy` is `no-cache` or `cache-and-network`, which also guarantee a network request). Calling this function will cause the component to re-suspend, , unless the call site is wrapped in `startTransition`.
`fetchMore` `({ query?: DocumentNode, variables?: TVariables, updateQuery: Function}) => Promise<ApolloQueryResult>`	A function that helps you fetch the next set of results for a paginated list field. Calling this function will cause the component to re-suspend, unless the call site is wrapped in `startTransition`.
`subscribeToMore` `(options: { document: DocumentNode, variables?: TVariables, updateQuery?: Function, onError?: Function}) => () => void`	A function that enables you to execute a subscription, usually to subscribe to specific fields that were included in the query. This function returns another function that you can call to terminate the subscription.

Hooks

Testing