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# ProcessInfo.ThermalStateDidChangeMessage

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

```
struct ThermalStateDidChangeMessage
```

## Overview

To observe this message, access the [`thermalState`](/documentation/Foundation/ProcessInfo/thermalState-swift.property) property prior to adding your observer.

Observe this message with the identifier [`thermalStateDidChange`](/documentation/Foundation/NotificationCenter/MessageIdentifier/thermalStateDidChange), or specify its type directly to the `addObserver(of:for:using:)` method.
The [`Subject`](/documentation/Foundation/NotificationCenter/MainActorMessage/Subject) of this message type is [`ProcessInfo`](/documentation/Foundation/ProcessInfo).

This message interoperates with the notification [`thermalStateDidChangeNotification`](/documentation/Foundation/ProcessInfo/thermalStateDidChangeNotification).
The system notifies observers of the message when the [`NotificationCenter`](/documentation/Foundation/NotificationCenter) posts the notification.
Similarly, the system notifies observers of the notification when it posts the message.

## Topics

### Creating a message

[`init()`](/documentation/Foundation/ProcessInfo/ThermalStateDidChangeMessage/init())

Creates a message about a thermal state change.

## Relationships

### Conforms To

[`Sendable`](/documentation/Swift/Sendable)

[`SendableMetatype`](/documentation/Swift/SendableMetatype)

[`AsyncMessage`](/documentation/Foundation/NotificationCenter/AsyncMessage)

---

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