---
title: "providePreview(for:completionHandler:)"
framework: quicklook
role: symbol
role_heading: Instance Method
path: "quicklook/qlpreviewingcontroller/providepreview(for:completionhandler:)"
---

# providePreview(for:completionHandler:)

## Declaration

```swift
optional func providePreview(for request: QLFilePreviewRequest, completionHandler handler: @escaping @Sendable (QLPreviewReply?, (any Error)?) -> Void)
```

```swift
optional func providePreview(for request: QLFilePreviewRequest) async throws -> QLPreviewReply
```

## Parameters

- `request`: An object which contains information about the preview that should be provided. It contains the URL of the file to provide a preview for.
- `handler`: Call the completion handler with a QLPreviewReply if you can provide a preview, or with an NSError if you cannot. If an error is passed or reply is nil, a generic preview will be provided instead. The handler can be called asynchronously after the method has returned.

## Discussion

Discussion Use this method to provide a QLPreviewReply that provides preview in the form of NSData, NSURL, PDFDocument, or a drawing into a context.