---
title: undoManager
framework: appkit
role: symbol
role_heading: Instance Property
path: appkit/nsdocument/undomanager
---

# undoManager

The object that the document uses to support undo/redo operations.

## Declaration

```swift
var undoManager: UndoManager? { get set }
```

## Discussion

Discussion When the hasUndoManager property is true, accessing this property creates an UndoManager before returning it. If the hasUndoManager property is false, the value of this property is nil by default. Assigning an undo manager to this property stores a reference to the object and automatically changes the hasUndoManager property to true. Whether you assign an undo manager or let the document create one, the document registers itself as an observer of various  UndoManager notifications so that appropriate document actions are stored on the undo stack.

## See Also

### Managing Undo and Redo Actions

- [hasUndoManager](appkit/nsdocument/hasundomanager.md)