DataScannerViewController

Recognize live text and machine-readable codes with VisionKit.

One.iOS.DataScannerViewController wraps VisionKit’s live data scanner on iOS. Check the SDK’s isSupported and isAvailable before presenting. Set ios.infoPlist.NSCameraUsageDescription. Recognition requires supported physical hardware; the simulator reports unsupported.

import { One } from 'one'

const Scanner = One.iOS.DataScannerViewController
if (Scanner.isSupported && Scanner.isAvailable) {
  const scanner = new Scanner({
    recognizedDataTypes: [Scanner.RecognizedDataType.text(), Scanner.RecognizedDataType.barcode()],
    recognizesMultipleItems: true,
  })
  scanner.delegate = {
    dataScanner: (sender, event) => {
      if ('didTapOn' in event) {
        sender.stopScanning()
        void sender.dismiss()
      }
    },
  }
  await scanner.present()
  scanner.startScanning()
  for await (const items of scanner.recognizedItems) {
    // consume each native batch in SDK reading order.
    if (items.length > 0) break
  }
  scanner.stopScanning()
  await scanner.dismiss()
}

The initializer uses an options object for Swift’s labeled arguments. The recognized-data-type set is an array deduplicated by the native SDK. RecognizedDataType.text(languages = [], textContentType?) and RecognizedDataType.barcode(symbologies = []) mirror the SDK factories. Barcode symbologies use Vision raw string values, such as QR. Text content types are dateTimeDuration, emailAddress, flightNumber, fullStreetAddress, shipmentTrackingNumber, telephoneNumber, URL, and currency.

recognizedItems is an AsyncIterable<RecognizedItem[]> backed by the native AsyncStream. Each iterator owns a subscription; breaking a for await loop cancels it. Consumers using next() directly must call return() to cancel. It delivers complete ordered batches, including empty batches, without fabricating recognition or deriving snapshots from delegate callbacks. stopScanning() pauses recognition; cancellation of iteration is separate.

Delegate labeled overloads adapt to dataScanner(sender, event) with didTapOn, didAdd, didUpdate, didRemove, or becameUnavailableWithError. Add/update/remove events include allItems. dataScannerDidZoom(sender) preserves the separate SDK method. Unavailability preserves unsupported and cameraRestricted enum cases; operation rejection uses E_DATA_SCANNER_UNSUPPORTED and E_DATA_SCANNER_CAMERA_RESTRICTED.

Recognized items are tagged objects with type, UUID-string id, and bounds containing topLeft, topRight, bottomRight, bottomLeft points. Text items have transcript; barcodes have optional payloadStringValue. The native Vision observation objects and UIKit overlayContainerView are not bound. This is a scanner subset, not the complete Vision or UIView API.

present and dismiss adapt UIViewController ownership to the app’s current presenter. They resolve after the transition. Start scanning explicitly after presentation. Dismissal stops scanning; a delegate event does not dismiss the scanner. capturePhoto() returns the same native UIImage encoding subset as document camera, with PNG/JPEG ArrayBuffer output. regionOfInterest is a CGRect-shaped { x, y, width, height } in view points; undefined clears it. Zoom factors use SDK units.

All configuration properties are readonly after initialization. Except for recognizedDataTypes, initializer fields are optional and use the defaults above.

Sources: DataScannerViewController, recognizedItems. Simulator unsupported rejection is covered by a fixture and production Swift SDK probe. Generated Nitro ABI integration and physical text/barcode recognition, tracking, taps, zoom, capture and permissions remain acceptance gates under the native CI owner.