swift 16进制转颜色

import Foundation

extension UIColor{
    
    /// 随机色
    static var randomColor:UIColor{
        get{
            let red = CGFloat(arc4random()%256)/255.0
            let green = CGFloat(arc4random()%256)/255.0
            let blue = CGFloat(arc4random()%256)/255.0
            return UIColor(red: red, green: green, blue: blue, alpha: 1.0)
        }
    }
   
 
    /// 16进制字符串转颜色
    /// - Parameter hex: 16进制字符串
    public convenience init(hex: String) {

            var red:   CGFloat = 0.0
            var green: CGFloat = 0.0
            var blue:  CGFloat = 0.0
            var alpha: CGFloat = 1.0
            var hex:   String = hex

            if hex.hasPrefix("#") {
                let index = hex.index(hex.startIndex, offsetBy: 1)
                hex = String(hex[index...])
            }

            let scanner = Scanner(string: hex)
            var hexValue: CUnsignedLongLong = 0
            if scanner.scanHexInt64(&hexValue) {
                switch (hex.count) {
                case 3:
                    red   = CGFloat((hexValue & 0xF00) >> 8)       / 15.0
                    green = CGFloat((hexValue & 0x0F0) >> 4)       / 15.0
                    blue  = CGFloat(hexValue & 0x00F)              / 15.0
                case 4:
                    red   = CGFloat((hexValue & 0xF000) >> 12)     / 15.0
                    green = CGFloat((hexValue & 0x0F00) >> 8)      / 15.0
                    blue  = CGFloat((hexValue & 0x00F0) >> 4)      / 15.0
                    alpha = CGFloat(hexValue & 0x000F)             / 15.0
                case 6:
                    red   = CGFloat((hexValue & 0xFF0000) >> 16)   / 255.0
                    green = CGFloat((hexValue & 0x00FF00) >> 8)    / 255.0
                    blue  = CGFloat(hexValue & 0x0000FF)           / 255.0
                case 8:
                    red   = CGFloat((hexValue & 0xFF000000) >> 24) / 255.0
                    green = CGFloat((hexValue & 0x00FF0000) >> 16) / 255.0
                    blue  = CGFloat((hexValue & 0x0000FF00) >> 8)  / 255.0
                    alpha = CGFloat(hexValue & 0x000000FF)         / 255.0
                default:
                    print("Invalid RGB string, number of characters after '#' should be either 3, 4, 6 or 8", terminator: "")
                }
            } else {
                print("Scan hex error")
            }
            self.init(red:red, green:green, blue:blue, alpha:alpha)
        }
}