Generate A QR Code

QRCodeGeneration.swift

//
//  QRCodeGeneration.swift
//  TempCheck
//
//  Created by Kraig Spear on 6/12/20.
//

import CoreImage.CIFilterBuiltins
import UIKit

/// Type that can generate a QRCode from a string
protocol QRCodeGeneratable {
    /**
     Generate a QRCode from a string
     - parameter from: String to generate a QRCode from
     - returns: Image of QRCode or xmark.circle if there were any errors creating the QRCode
     */
    func generate(from string: String) -> UIImage
}

/**
 Implementation of `QRCodeGeneratable`
 Generates a QRCode from a String
 */
final class QRCodeGeneration: QRCodeGeneratable {
    
    /**
    Generate a QRCode from a string
    - parameter from: String to generate a QRCode from
    - returns: Image of QRCode or xmark.circle if there were any errors creating the QRCode
    */
    func generate(from string: String) -> UIImage {
        let context = CIContext()
        let filter = CIFilter.qrCodeGenerator()

        let data = Data(string.utf8)
        filter.setValue(data, forKey: "inputMessage")

        if let outputImage = filter.outputImage {
            if let cgimg = context.createCGImage(outputImage, from: outputImage.extent) {
                return UIImage(cgImage: cgimg)
            }
        }

        return UIImage(systemName: "xmark.circle") ?? UIImage()
    }
}