---
title: "updateValue(_:for:onSubscribedCentrals:)"
framework: corebluetooth
role: symbol
role_heading: Instance Method
path: "corebluetooth/cbperipheralmanager/updatevalue(_:for:onsubscribedcentrals:)"
---

# updateValue(_:for:onSubscribedCentrals:)

Send an updated characteristic value to one or more subscribed centrals, using a notification or indication.

## Declaration

```swift
func updateValue(_ value: Data, for characteristic: CBMutableCharacteristic, onSubscribedCentrals centrals: [CBCentral]?) -> Bool
```

## Parameters

- `value`: The characteristic value you want to send via a notification or indication.
- `characteristic`: The characteristic whose value has changed.
- `centrals`: A list of centrals (represented by doc://com.apple.corebluetooth/documentation/CoreBluetooth/CBCentral objects) that have subscribed to receive updates of the characteristic’s value. If nil, the manager updates all subscribed centrals. The manager ignores any centrals that haven’t subscribed to the characteristic’s value.

## Return Value

Return Value This value is true if the update is successfully sent to the subscribed central or centrals. false if the update isn’t successfully sent because the underlying transmit queue is full.

## Discussion

Discussion You use this method to send updates of a characteristic’s value—through a notification or indication—to selected centrals that have subscribed to that characteristic’s value. If the method returns false because the underlying transmit queue is full, the peripheral manager calls the peripheralManagerIsReady(toUpdateSubscribers:) method of its delegate object when more space in the transmit queue becomes available. After you receive this delegate method callback, you may resend the update. If the length of the value parameter exceeds the length of the maximumUpdateValueLength property of a subscribed CBCentral, the value parameter truncates accordingly.