| --- |
| id: paginated-queries |
| title: Paginated / Lagged Queries |
| ref: docs/framework/react/guides/paginated-queries.md |
| replace: |
| { |
| 'useQuery': 'injectQuery', |
| 'useInfiniteQuery': 'injectInfiniteQuery', |
| 'hook': 'function', |
| } |
| --- |
| |
| [//]: # 'Example' |
|
|
| ```ts |
| const result = injectQuery(() => ({ |
| queryKey: ['projects', page()], |
| queryFn: fetchProjects, |
| })) |
| ``` |
|
|
| [//]: # 'Example' |
| [//]: # 'Example2' |
|
|
| ```angular-ts |
| @Component({ |
| selector: 'pagination-example', |
| template: ` |
| <div> |
| <p> |
| In this example, each page of data remains visible as the next page is |
| fetched. The buttons and capability to proceed to the next page are also |
| suppressed until the next page cursor is known. Each page is cached as a |
| normal query too, so when going to previous pages, you'll see them |
| instantaneously while they are also re-fetched invisibly in the |
| background. |
| </p> |
| @if (query.status() === 'pending') { |
| <div>Loading...</div> |
| } @else if (query.status() === 'error') { |
| <div>Error: {{ query.error().message }}</div> |
| } @else { |
| <!-- 'data' will either resolve to the latest page's data --> |
| <!-- or if fetching a new page, the last successful page's data --> |
| <div> |
| @for (project of query.data().projects; track project.id) { |
| <p>{{ project.name }}</p> |
| } |
| </div> |
| } |
| |
| <div>Current Page: {{ page() + 1 }}</div> |
| <button (click)="previousPage()" [disabled]="page() === 0"> |
| Previous Page |
| </button> |
| <button |
| (click)="nextPage()" |
| [disabled]="query.isPlaceholderData() || !query.data()?.hasMore" |
| > |
| Next Page |
| </button> |
| <!-- Since the last page's data potentially sticks around between page requests, --> |
| <!-- we can use 'isFetching' to show a background loading --> |
| <!-- indicator since our status === 'pending' state won't be triggered --> |
| @if (query.isFetching()) { |
| <span> Loading...</span> |
| } |
| </div> |
| `, |
| }) |
| export class PaginationExampleComponent { |
| page = signal(0) |
| queryClient = inject(QueryClient) |
| |
| query = injectQuery(() => ({ |
| queryKey: ['projects', this.page()], |
| queryFn: () => lastValueFrom(fetchProjects(this.page())), |
| placeholderData: keepPreviousData, |
| staleTime: 5000, |
| })) |
| |
| constructor() { |
| effect(() => { |
| // Prefetch the next page! |
| if (!this.query.isPlaceholderData() && this.query.data()?.hasMore) { |
| this.#queryClient.prefetchQuery({ |
| queryKey: ['projects', this.page() + 1], |
| queryFn: () => lastValueFrom(fetchProjects(this.page() + 1)), |
| }) |
| } |
| }) |
| } |
| |
| previousPage() { |
| this.page.update((old) => Math.max(old - 1, 0)) |
| } |
| |
| nextPage() { |
| this.page.update((old) => (this.query.data()?.hasMore ? old + 1 : old)) |
| } |
| } |
| ``` |
|
|
| [//]: # 'Example2' |
|
|
