Is there a way to generate QR code image on iOS

Question

Is there a standard way to generate a QR code and attach it to a mail item from iOS client app (no server code)?

Answer 1

It has been a while since this question was asked and a number of almost perfect answers have been given already. However I had to tweak and combine several answers to get it working perfectly for AppleTV 4K, iPhone X and iPadPro using Xcode 9.2 in 2018. Here's the code if anyone needs it.

@IBOutlet weak var qrCodeBox: UIImageView!

func createQRFromString(_ str: String, size: CGSize) -> UIImage {
    let stringData = str.data(using: .utf8)

  let qrFilter = CIFilter(name: "CIQRCodeGenerator")!
  qrFilter.setValue(stringData, forKey: "inputMessage")
  qrFilter.setValue("H", forKey: "inputCorrectionLevel")

  let minimalQRimage = qrFilter.outputImage!
  // NOTE that a QR code is always square, so minimalQRimage..width === .height
  let minimalSideLength = minimalQRimage.extent.width

  let smallestOutputExtent = (size.width < size.height) ? size.width : size.height
  let scaleFactor = smallestOutputExtent / minimalSideLength
  let scaledImage = minimalQRimage.transformed(
    by: CGAffineTransform(scaleX: scaleFactor, y: scaleFactor))

  return UIImage(ciImage: scaledImage, 
                 scale: UIScreen.main.scale, 
                 orientation: .up)
}

override func viewDidLoad() {
    super.viewDidLoad()
    let myQRimage = createQRFromString("https://www.apple.com", 
                      size: qrCodeBox.frame.size)
    qrCodeBox.image = myQRimage
}