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a7e7934505
* [ACA-4729] Add infinite scroll to version list * [ACA-4729] CR fixes * [ACA-4729] CR fixes * [ACA-4729] Items count fix for infinite scroll datasource
67 lines
3.3 KiB
Markdown
67 lines
3.3 KiB
Markdown
---
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Title: Infinite Scroll Datasource
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Added: v6.6.0
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Status: Active
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Last reviewed: 2024-01-15
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---
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# [Infinite Scroll Datasource](../../../lib/content-services/src/lib/infinite-scroll-datasource/infinite-scroll-datasource.ts "Defined in infinite-scroll-datasource.ts")
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Contains abstract class acting as a baseline for various datasources for infinite scrolls.
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## Basic Usage
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First step to use infinite scroll datasource in any component is creating a datasource class extending `InfiniteScrollDatasource` using specific source of data e.g. one of the content endpoints.
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```ts
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export class VersionListDataSource extends InfiniteScrollDatasource<VersionEntry> {
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constructor(private versionsApi: VersionsApi, private node: Node) {
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super();
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}
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getNextBatch(pagingOptions: ContentPagingQuery): Observable<VersionEntry[]> {
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return from(this.versionsApi.listVersionHistory(this.node.id, pagingOptions)).pipe(
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take(1),
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map((versionPaging) => versionPaging.list.entries)
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);
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}
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}
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```
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Then in component that will have the infinite scroll define the datasource as instance of a class created in previous step, optionally you can set custom size of the items batch or listen to loading state changes:
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```ts
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this.versionsDataSource = new VersionListDataSource(this.versionsApi, this.node);
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this.versionsDataSource.batchSize = 50;
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this.versionsDataSource.isLoading.pipe(takeUntil(this.onDestroy$)).subscribe((isLoading) => this.isLoading = isLoading);
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```
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Final step is to add the [CdkVirtualScrollViewport](https://material.angular.io/cdk/scrolling/api#CdkVirtualScrollViewport) with [CdkVirtualFor](https://material.angular.io/cdk/scrolling/api#CdkVirtualForOf) loop displaying items from the datasource.
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```html
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<cdk-virtual-scroll-viewport appendOnly itemSize="88">
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<div *cdkVirtualFor="let version of versionsDataSource"></div>
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</cdk-virtual-scroll-viewport>
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```
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When user will scroll down to the bottom of the list next batch of items will be fetched until all items are visible.
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## Class members
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### Properties
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| Name | Type | Default value | Description |
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| ---- | ---- | ------------- | ----------- |
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| batchSize | `number` | 100 | Determines how much items will be fetched within one batch. |
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| firstItem | `T` | | Returns the first item ever fetched. |
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| isLoading | [`Observable`](https://rxjs.dev/api/index/class/Observable)`<boolean>` | | Observable representing the state of loading the first batch. |
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| itemsCount | `number` | | Number of items fetched so far. |
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### Methods
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- **connect**(collectionViewer: [`CollectionViewer`](https://material.angular.io/cdk/collections/api)): [`Observable`](https://rxjs.dev/api/index/class/Observable)`<T>`<br/>
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Called by the virtual scroll viewport to receive a stream that emits the data array that should be rendered.
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- collectionViewer:_ [`CollectionViewer`](https://material.angular.io/cdk/collections/api) - collection viewer providing view changes that are listened to so that next batch can be fetched
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- **Returns** [`Observable`](https://rxjs.dev/api/index/class/Observable)`<T>` - Data stream containing fetched items.
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- **disconnect**(): void<br/>
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Called when viewport is destroyed, disconnects the datasource, unsubscribes from the view changes.
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- **reset**(): void<br/>
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Resets the datasource by fetching the first batch.
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