# useSelectedBlocks

Source: https://sdk.pdf.net/docs/v1/reference/useSelectedBlocks



Returns the currently selected blocks as snapshots and re-renders the component when the selection, or a selected block itself, changes.

```ts
const selectedBlocks = useSelectedBlocks() // readonly Block[]
```

* The entries are `Block` snapshots: plain objects describing each block at the moment of reading. A snapshot doesn't update with the document, and changing it doesn't change the document; apply changes through the command hooks, such as [useSetWidgetProps](https://sdk.pdf.net/docs/v1/reference/useSetWidgetProps).
* The array reference changes whenever the content changes, so `useEffect` on it handles selection changes imperatively.
* When only the selection itself matters, not the block content, [useSelection](https://sdk.pdf.net/docs/v1/reference/useSelection) re-renders less often. To read the selected blocks inside an event handler, use [useSelectedBlocksGetter](https://sdk.pdf.net/docs/v1/reference/useSelectedBlocksGetter).

## Block kinds [#block-kinds]

`Block` is a union told apart by `type` and `subtype`. Every block carries a session-scoped `id` and its `pageId`.

| Kind              | Discriminator                             | Fields                                                                                                                       |
| ----------------- | ----------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------- |
| `Widget`          | `type: 'annotation'`, `subtype: 'Widget'` | `widgetType` and the widget properties listed in [useSetWidgetProps](https://sdk.pdf.net/docs/v1/reference/useSetWidgetProps).                  |
| `InkAnnotation`   | `type: 'annotation'`, `subtype: 'Ink'`    | The ink properties listed in [useInkAnnotationCreate](https://sdk.pdf.net/docs/v1/reference/useInkAnnotationCreate).                            |
| `StampAnnotation` | `type: 'annotation'`, `subtype: 'Stamp'`  | The box and `imageId`, described in [useStampAnnotationCreate](https://sdk.pdf.net/docs/v1/reference/useStampAnnotationCreate).                 |
| `UnknownBlock`    | `type: 'unknown'`                         | Only `id` and `pageId`. Paragraphs and the annotation kinds without a dedicated snapshot type yet, such as shapes and lines. |

## Example [#example]

```tsx
import { useSelectedBlocks } from '@sdk-pdf/react'

function SelectionSummary() {
  const selectedBlocks = useSelectedBlocks()

  if (selectedBlocks.length === 0) return null

  const widgetCount = selectedBlocks.filter(
    (block) => block.type === 'annotation' && block.subtype === 'Widget'
  ).length

  return (
    <span>
      {selectedBlocks.length} selected, {widgetCount} form fields
    </span>
  )
}
```