---
title: UndoManager.CheckpointMessage
framework: foundation
role: symbol
role_heading: Structure
path: foundation/undomanager/checkpointmessage
---

# UndoManager.CheckpointMessage

A message that an undo manager sends at certain checkpoints.

## Declaration

```swift
struct CheckpointMessage
```

## Overview

Overview The undo manager posts this message when it opens or closes an undo group (except when it opens a top-level group) and when it checks the redo stack. Observe this message type with the identifier checkpoint, or specify its type directly to the addObserver(of:for:using:) method. The Subject of this message type is UndoManager. This message interoperates with the notification NSUndoManagerCheckpoint. The system notifies observers of the message when the NotificationCenter posts the notification. Similarly, the system notifies observers of the notification when it posts the message.

## Topics

### Initializers

- [init()](foundation/undomanager/checkpointmessage/init().md)

## Relationships

### Conforms To

- [NotificationCenter.MainActorMessage](foundation/notificationcenter/mainactormessage.md)
- [Sendable](swift/sendable.md)
- [SendableMetatype](swift/sendablemetatype.md)

## See Also

### Working with notification messages

- [UndoManager.WillUndoChangeMessage](foundation/undomanager/willundochangemessage.md)
- [UndoManager.DidUndoChangeMessage](foundation/undomanager/didundochangemessage.md)
- [UndoManager.WillRedoChangeMessage](foundation/undomanager/willredochangemessage.md)
- [UndoManager.DidRedoChangeMessage](foundation/undomanager/didredochangemessage.md)
- [UndoManager.DidOpenUndoGroupMessage](foundation/undomanager/didopenundogroupmessage.md)
- [UndoManager.WillCloseUndoGroupMessage](foundation/undomanager/willcloseundogroupmessage.md)
- [UndoManager.DidCloseUndoGroupMessage](foundation/undomanager/didcloseundogroupmessage.md)