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# scannerDevice(_:didSelect:error:)

Tells the client when a functional unit is selected on the scanner.

```
optional func scannerDevice(_ scanner: ICScannerDevice, didSelect functionalUnit: ICScannerFunctionalUnit, error: (any Error)?)
```

## Discussion

A functional unit is selected immediately after the scanner instantiates and in response to calling [`requestSelect(_:)`](/documentation/ImageCaptureCore/ICScannerDevice/requestSelect(_:)).

---

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