Swift 5 UIColor+hexString - Accepts RGB/RRGGBB/RRGGBBAA

UIColor+hexString.swift

import Foundation
import UIKit

extension UIColor {
  convenience init(hexString: String) {
    
    var hexString: String = hexString.trimmingCharacters(in: CharacterSet.whitespacesAndNewlines)
    
    if (hexString.hasPrefix("#")) {
      hexString.removeFirst()
    }
    
    if hexString.count == 3 {
      var fullString = ""
      for char in hexString {
        fullString.append(char)
        fullString.append(char)
      }
      hexString = fullString
    }
    
    if hexString.count == 6 {
      hexString.append("FF")
    }
    
    assert(hexString.count == 8, "invalid hex string used to init UIColor")
    
    let scanner = Scanner(string: hexString)
    var color: UInt64 = 0
    scanner.scanHexInt64(&color)
    let mask = 0x00000000FF
    let r = Int(color >> 24) & mask
    let g = Int(color >> 16) & mask
    let b = Int(color >> 8) & mask
    let a = Int(color) & mask
    let red   = CGFloat(r) / 255.0
    let green = CGFloat(g) / 255.0
    let blue  = CGFloat(b) / 255.0
    let alpha = CGFloat(a) / 255.0
    self.init(red:red, green:green, blue:blue, alpha:alpha)
  }
  
  func toHexString() -> String {
    var r:CGFloat = 0
    var g:CGFloat = 0
    var b:CGFloat = 0
    var a:CGFloat = 0
    getRed(&r, green: &g, blue: &b, alpha: &a)
    let rgb:Int = (Int)(r*255)<<16 | (Int)(g*255)<<8 | (Int)(b*255)<<0
    return String(format:"#%06x", rgb)
  }
  
  func toHexStringWithAlpha() -> String {
    var r:CGFloat = 0
    var g:CGFloat = 0
    var b:CGFloat = 0
    var a:CGFloat = 0
    getRed(&r, green: &g, blue: &b, alpha: &a)
    let rgba:Int = (Int)(r*255)<<24 | (Int)(g*255)<<16 | (Int)(b*255)<<8 | (Int)(a*255)<<0
    return String(format:"#%06x", rgba)
  }
}

after displayed, the color value is incorrect