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# CBCentralManagerOptionRestoreIdentifierKey

A string containing a unique identifier (UID) for the central manager to instantiate.

```
let CBCentralManagerOptionRestoreIdentifierKey: String
```

## Discussion

The value for this key is an <doc://com.apple.documentation/documentation/Foundation/NSString>. The system uses this UID to identify a specific [`CBCentralManager`](/documentation/CoreBluetooth/CBCentralManager), so the UID must be identical across executions of the app.

In scene-based apps that adopt <doc://com.apple.documentation/documentation/UIKit/UISceneDelegate>, `launchOptions` is always `nil` on launch, so `UIApplicationLaunchOptionsBluetoothCentralsKey` is not available to deliver identifiers. Persist the UID yourself (for example, in <doc://com.apple.documentation/documentation/Foundation/UserDefaults>) and pass it to [`init(delegate:queue:options:)`](/documentation/CoreBluetooth/CBCentralManager/init(delegate:queue:options:)) on every launch.

Providing this key causes Core Bluetooth to call [`centralManager(_:willRestoreState:)`](/documentation/CoreBluetooth/CBCentralManagerDelegate/centralManager(_:willRestoreState:)) with the preserved state when restoration is available. For a description of the state dictionary keys your delegate receives, see [Central Manager State Restoration Options](/documentation/CoreBluetooth/central-manager-state-restoration-options).

---

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