swift中。#f5f5f5 该如何展示出颜色

extension UIColor {

convenience init(hexString: String) {

let hex = hexString.trimmingCharacters(in: CharacterSet.alphanumerics.inverted)

var int = UInt32()

Scanner(string: hex).scanHexInt32(&int)

let a, r, g, b: UInt32

switch hex.characters.count {

case 3: // RGB (12-bit)

(a, r, g, b) = (255, (int >> 8) * 17, (int >> 4 & 0xF) * 17, (int & 0xF) * 17)

case 6: // RGB (24-bit)

(a, r, g, b) = (255, int >> 16, int >> 8 & 0xFF, int & 0xFF)

case 8: // ARGB (32-bit)

(a, r, g, b) = (int >> 24, int >> 16 & 0xFF, int >> 8 & 0xFF, int & 0xFF)

default:

(a, r, g, b) = (255, 0, 0, 0)

}

self.init(red: CGFloat(r) / 255, green: CGFloat(g) / 255, blue: CGFloat(b) / 255, alpha: CGFloat(a) / 255)

}

}