QRCodeExample.swift

import UIKit
import CoreImage

func createQRFromString(str: String) -> CIImage? {
    let stringData = str.data(using: .utf8) as? NSData
    
    guard let f1 = CIFilter(name: "CIQRCodeGenerator") else {
        return nil
    }
    
    f1.setValue(stringData, forKey: "inputMessage")
    f1.setValue("H", forKey: "inputCorrectionLevel")
    
    return f1.outputImage?.transformed(by: CGAffineTransform(scaleX: 5.0, y: 5.0))
}

if let img = createQRFromString(str: "") {
    let ctx = CIContext(options:nil)
    if let cgImage = ctx.createCGImage(img, from: img.extent) {
        let imageView = UIImageView(frame: CGRect(x: 0, y: 0, width: 256, height: 256))
        imageView.contentMode = .center
        imageView.image = UIImage(cgImage: cgImage)
    }
}