如何在Swift中创建十六进制颜色字符串UIColor初始化程序？[重复]

Xpre 9•Swift 4或更高版本

extension UIColor {    convenience init?(hexaRGB: String, alpha: CGFloat = 1) {        var chars = Array(hexaRGB.hasPrefix("#") ? hexaRGB.dropFirst() : hexaRGB[...])        switch chars.count {        case 3: chars = chars.flatMap { [$0, $0] }        case 6: break        default: return nil        }        self.init(red: .init(strtoul(String(chars[0...1]), nil, 16)) / 255,     green: .init(strtoul(String(chars[2...3]), nil, 16)) / 255,      blue: .init(strtoul(String(chars[4...5]), nil, 16)) / 255,     alpha: alpha)    }    convenience init?(hexaRGBA: String) {        var chars = Array(hexaRGBA.hasPrefix("#") ? hexaRGBA.dropFirst() : hexaRGBA[...])        switch chars.count {        case 3: chars = chars.flatMap { [$0, $0] }; fallthrough        case 6: chars.append(contentsOf: ["F","F"])        case 8: break        default: return nil        }        self.init(red: .init(strtoul(String(chars[0...1]), nil, 16)) / 255,     green: .init(strtoul(String(chars[2...3]), nil, 16)) / 255,      blue: .init(strtoul(String(chars[4...5]), nil, 16)) / 255,     alpha: .init(strtoul(String(chars[6...7]), nil, 16)) / 255)    }    convenience init?(hexaARGB: String) {        var chars = Array(hexaARGB.hasPrefix("#") ? hexaARGB.dropFirst() : hexaARGB[...])        switch chars.count {        case 3: chars = chars.flatMap { [$0, $0] }; fallthrough        case 6: chars.append(contentsOf: ["F","F"])        case 8: break        default: return nil        }        self.init(red: .init(strtoul(String(chars[2...3]), nil, 16)) / 255,     green: .init(strtoul(String(chars[4...5]), nil, 16)) / 255,      blue: .init(strtoul(String(chars[6...7]), nil, 16)) / 255,     alpha: .init(strtoul(String(chars[0...1]), nil, 16)) / 255)    }}

if let textColor = UIColor(hexa: "00F") {    print(textColor) // r 0.0 g 0.0 b 1.0 a 1.0}

if let textColor = UIColor(hexaRGB: "00F") {    print(textColor) // r 0.0 g 0.0 b 1.0 a 1.0}UIColor(hexaRGB: "#00F")       // r 0.0 g 0.0 b 1.0 a 1.0UIColor(hexaRGB: "#00F", alpha: 0.5)      // r 0.0 g 0.0 b 1.0 a 0.5UIColor(hexaRGB: "#0000FF")    // r 0.0 g 0.0 b 1.0 a 1.0UIColor(hexaRGB: "#0000FF", alpha: 0.5)   // r 0.0 g 0.0 b 1.0 a 0.5UIColor(hexaRGBA: "#0000FFFF") // r 0.0 g 0.0 b 1.0 a 1.0UIColor(hexaRGBA: "#0000FF7F") // r 0.0 g 0.0 b 1.0 a 0.498UIColor(hexaARGB: "#FF0000FF") // r 0.0 g 0.0 b 1.0 a 1.0UIColor(hexaARGB: "#7F0000FF") // r 0.0 g 0.0 b 1.0 a 0.498