| --- |
| id: placeholder-query-data |
| title: Placeholder Query Data |
| ref: docs/framework/react/guides/placeholder-query-data.md |
| --- |
| |
| [//]: # 'ExampleValue' |
|
|
| ```ts |
| class TodosComponent { |
| result = injectQuery(() => ({ |
| queryKey: ['todos'], |
| queryFn: () => fetch('/todos'), |
| placeholderData: placeholderTodos, |
| })) |
| } |
| ``` |
|
|
| [//]: # 'ExampleValue' |
| [//]: # 'Memoization' |
| [//]: # 'Memoization' |
| [//]: # 'ExampleFunction' |
|
|
| ```ts |
| class TodosComponent { |
| result = injectQuery(() => ({ |
| queryKey: ['todos', id()], |
| queryFn: () => fetch(`/todos/${id}`), |
| placeholderData: (previousData, previousQuery) => previousData, |
| })) |
| } |
| ``` |
|
|
| [//]: # 'ExampleFunction' |
| [//]: # 'ExampleCache' |
|
|
| ```ts |
| export class BlogPostComponent { |
| // Until Angular supports signal-based inputs, we have to set a signal |
| @Input({ required: true, alias: 'postId' }) |
| set _postId(value: number) { |
| this.postId.set(value) |
| } |
| postId = signal(0) |
| queryClient = inject(QueryClient) |
| |
| result = injectQuery(() => ({ |
| queryKey: ['blogPost', this.postId()], |
| queryFn: () => fetch(`/blogPosts/${this.postId()}`), |
| placeholderData: () => { |
| // Use the smaller/preview version of the blogPost from the 'blogPosts' |
| // query as the placeholder data for this blogPost query |
| return queryClient |
| .getQueryData(['blogPosts']) |
| ?.find((d) => d.id === this.postId()) |
| }, |
| })) |
| } |
| ``` |
|
|
| [//]: # 'ExampleCache' |
| [//]: # 'Materials' |
| [//]: # 'Materials' |
|
|
