---
title: "performAsynchronousFileAccess(_:)"
framework: uikit
role: symbol
role_heading: Instance Method
path: "uikit/uidocument/performasynchronousfileaccess(_:)"
---

# performAsynchronousFileAccess(_:)

Schedules a document-reading or document-writing operation on a concurrent background queue.

## Declaration

```swift
func performAsynchronousFileAccess(_ block: @escaping () -> Void)
```

## Parameters

- `block`: A block that’s invoked as the task to execute on the background queue. The block returns no value and takes no parameters.

## Discussion

Discussion A typical UIDocument subclass — one that overrides contents(forType:) and load(fromContents:ofType:) — doesn’t need to call this method. The default implementations of save(to:for:completionHandler:) and open(completionHandler:) call this method to serialize file access. If you override these methods and don’t call super, you should call this method to serialize file access on a background queue. If you directly call the read(from:) method, you should wrap that call in the block passed into performAsynchronousFileAccess(_:).