Capture machine-readable codes and text with VisionKit

4:40 - Creating a data scanner instance and present it

import VisionKit

// Specify the types of data to recognize
let recognizedDataTypes:Set<DataScannerViewController.RecognizedDataType> = [
    .barcode(symbologies: [.qr]),
  	// uncomment to filter on specific languages (e.g., Japanese)
    // .text(languages: ["ja"])
    // uncomment to filter on specific content types (e.g., URLs)
		// .text(textContentType: .URL)
]

// Create the data scanner, present it, and start scanning!
let dataScanner = DataScannerViewController(recognizedDataTypes: recognizedDataTypes)
present(dataScanner, animated: true) {
    try? dataScanner.startScanning()
}

8:11 - Set a delegate

// Specify the types of data to recognize
let recognizedDataTypes:Set<DataScannerViewController.RecognizedDataType> = [
    .barcode(symbologies: [.qr]),
    .text(textContentType: .URL)
]

// Create the data scanner, present it, and start scanning!
let dataScanner = DataScannerViewController(recognizedDataTypes: recognizedDataTypes)
dataScanner.delegate = self.present(dataScanner, animated: true) {
    try? dataScanner.startScanning()
}

8:19 - Handling tap interactions

func dataScanner(_ dataScanner: DataScannerViewController, didTapOn item: RecognizedItem) {
    switch item {
    case .text(let text):
        print("text: \(text.transcript)")
    case .barcode(let barcode):
        print("barcode: \(barcode.payloadStringValue ?? "unknown")")
    default:
        print("unexpected item")
    }
}

9:11 - Adding custom highlights via the didAdd delegate method

// Dictionary to store our custom highlights keyed by their associated item ID.
var itemHighlightViews: [RecognizedItem.ID: HighlightView] = [:]

// For each new item, create a new highlight view and add it to the view hierarchy.
func dataScanner(_ dataScanner: DataScannerViewController, didAdd addItems: [RecognizedItem], allItems: [RecognizedItem]) {
    for item in addedItems {
        let newView = newHighlightView(forItem: item)
        itemHighlightViews[item.id] = newView
        dataScanner.overlayContainerView.addSubview(newView)
    }
}

9:37 - Animating custom highlights during the didUpdate delegate method

// Animate highlight views to their new bounds
func dataScanner(_ dataScanner: DataScannerViewController, didUpdate updatedItems: [RecognizedItem], allItems: [RecognizedItem]) {
    for item in updatedItems {
        if let view = itemHighlightViews[item.id] {
            animate(view: view, toNewBounds: item.bounds)
        }
    }
}

10:03 - Removing custom highlights during the didRemove delegate callback

// Remove highlights when their associated items are removed.
func dataScanner(_ dataScanner: DataScannerViewController, didRemove removedItems: [RecognizedItem], allItems: [RecognizedItem]) {
    for item in removedItems {
        if let view = itemHighlightViews[item.id] {
            itemHighlightViews.removeValue(forKey: item.id)
            view.removeFromSuperview()
        }
    }
}

10:54 - Take a still photo and save it to the camera roll

// Take a still photo and save to the camera roll
if let image = try? await dataScanner.capturePhoto() {
    UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil)
}

11:10 - Using the recognizedItems async stream to keep track of items

// Send a notification when the recognized items change.
var currentItems: [RecognizedItem] = []

func updateViaAsyncStream() async {
    guard let scanner = dataScannerViewController else { return }
    
    let stream = scanner.recognizedItems
    for await newItems: [RecognizedItem] in stream {
        let diff = newItems.difference(from: currentItems) { a, b in
            return a.id == b.id
        }
        
        if !diff.isEmpty {
            currentItems = newItems
            sendDidChangeNotification()
        }
    }
}