<!--
{
  "availability" : [
    "iOS: 9.0.0 - 11.0.0",
    "iPadOS: 9.0.0 - 11.0.0",
    "macCatalyst: 13.1.0 - 13.1.0",
    "visionOS: 1.0.0 - 1.0.0"
  ],
  "documentType" : "symbol",
  "framework" : "HomeKit",
  "identifier" : "/documentation/HomeKit/HMCharacteristicEvent/updateTriggerValue(_:completionHandler:)",
  "metadataVersion" : "0.1.0",
  "role" : "Instance Method",
  "symbol" : {
    "kind" : "Instance Method",
    "modules" : [
      "HomeKit"
    ],
    "preciseIdentifier" : "c:objc(cs)HMCharacteristicEvent(im)updateTriggerValue:completionHandler:"
  },
  "title" : "updateTriggerValue(_:completionHandler:)"
}
-->

# updateTriggerValue(_:completionHandler:)

Changes the trigger value associated with this event.

```
func updateTriggerValue(_ triggerValue: TriggerValueType?, completionHandler completion: @escaping @Sendable ((any Error)?) -> Void)
```

## Parameters

`triggerValue`

The value of the characteristic that triggers the event.

`completion`

The block executed once the trigger value update request has been processed.

- error: `nil` on success; otherwise, error object indicating the reason for failure.

## Discussion

Set the trigger value to `nil` to trigger the event whenever the value of the characteristic changes.

---

Copyright &copy; 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)