---
title: ProcessInfo.ThermalStateDidChangeMessage
framework: foundation
role: symbol
role_heading: Structure
path: foundation/processinfo/thermalstatedidchangemessage
---

# ProcessInfo.ThermalStateDidChangeMessage

A message the system sends when the device’s thermal state changes.

## Declaration

```swift
struct ThermalStateDidChangeMessage
```

## Overview

Overview To observe this message, access the thermalState property prior to adding your observer. Observe this message with the identifier thermalStateDidChange, or specify its type directly to the addObserver(of:for:using:) method. The Subject of this message type is ProcessInfo. This message interoperates with the notification thermalStateDidChangeNotification. 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

### Creating a message

- [init()](foundation/processinfo/thermalstatedidchangemessage/init().md)

## Relationships

### Conforms To

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

## See Also

### Working with notification messsages

- [ProcessInfo.PowerStateDidChangeMessage](foundation/processinfo/powerstatedidchangemessage.md)