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# CBMutableDescriptor

An object that provides additional information about a local peripheral’s characteristic.

```
class CBMutableDescriptor
```

## Overview

You use the [`CBMutableDescriptor`](/documentation/CoreBluetooth/CBMutableDescriptor) class to create a local characteristic descriptor. After you create a descriptor and associate it with a local characteristic, you can publish it to the peripheral’s local database using the [`add(_:)`](/documentation/CoreBluetooth/CBPeripheralManager/add(_:)) method of the [`CBPeripheralManager`](/documentation/CoreBluetooth/CBPeripheralManager) class. This also publishes the characteristic and local service to which the descriptor belongs. After you publish a local descriptor, Core Bluetooth caches the descriptor and you can no longer make changes to it.

[`CBUUID`](/documentation/CoreBluetooth/CBUUID) details predefined descriptor types and their corresponding value types. That said, only two of these are currently supported when creating local, mutable descriptors: the characteristic user description descriptor and the characteristic format descriptor. [`CBUUID`](/documentation/CoreBluetooth/CBUUID) declares these as the constants [`CBUUIDCharacteristicUserDescriptionString`](/documentation/CoreBluetooth/CBUUIDCharacteristicUserDescriptionString) and [`CBUUIDCharacteristicFormatString`](/documentation/CoreBluetooth/CBUUIDCharacteristicFormatString), respectively. The system automatically creates the extended properties descriptor and the client configuration descriptor, depending on the properties of the characteristic to which the descriptor belongs.

## Topics

### Creating a Mutable Descriptor

[`-  initWithType:value:`](/documentation/CoreBluetooth/CBMutableDescriptor/init(type:value:))

Creates a mutable descriptor with a specified value.

## Relationships

### Conforms To

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

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

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

[`NSObjectProtocol`](/documentation/ObjectiveC/NSObjectProtocol)

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

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

### Inherits From

[`CBDescriptor`](/documentation/CoreBluetooth/CBDescriptor)

---

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