UIColor扩展，这将大大帮助你!(4.0版本:斯威夫特)

import UIKit
extension UIColor {
/// rgb颜色
convenience init(r: CGFloat, g: CGFloat, b: CGFloat) {
    self.init(red: r/255.0 ,green: g/255.0 ,blue: b/255.0 ,alpha:1.0)
}

/// 纯色（用于灰色）
convenience init(gray: CGFloat) {
    self.init(red: gray/255.0 ,green: gray/255.0 ,blue: gray/255.0 ,alpha:1.0)
}
/// 随机色
class func randomCGColor() -> UIColor {
    return UIColor(r: CGFloat(arc4random_uniform(256)), g: CGFloat(arc4random_uniform(256)), b: CGFloat(arc4random_uniform(256)))
}

/// hex颜色-Int
convenience init(hex:Int, alpha:CGFloat = 1.0) {
    self.init(
        red:   CGFloat((hex & 0xFF0000) >> 16) / 255.0,
        green: CGFloat((hex & 0x00FF00) >> 8)  / 255.0,
        blue:  CGFloat((hex & 0x0000FF) >> 0)  / 255.0,
        alpha: alpha
    )
}
/// hex颜色-String
convenience init(hexString: String){
    var red:   CGFloat = 0.0
    var green: CGFloat = 0.0
    var blue:  CGFloat = 0.0
    var alpha: CGFloat = 1.0
    let scanner = Scanner(string: hexString)
    var hexValue: CUnsignedLongLong = 0
    if scanner.scanHexInt64(&hexValue) {
        switch (hexString.characters.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:
            alpha = CGFloat((hexValue & 0xFF000000) >> 24) / 255.0
            red   = CGFloat((hexValue & 0x00FF0000) >> 16) / 255.0
            green = CGFloat((hexValue & 0x0000FF00) >> 8)  / 255.0
            blue  = CGFloat(hexValue & 0x000000FF)         / 255.0
        default:
            log.info("Invalid RGB string, number of characters after '#' should be either 3, 4, 6 or 8")
        }
    } else {
        log.error("Scan hex error")
    }
    self.init(red:red, green:green, blue:blue, alpha:alpha)
}}

带验证的十六进制

根据爱德华多的回答

细节

Xcode 10.0, Swift 4.2 Xcode 10.2.1 (10E1001)

解决方案

import UIKit

extension UIColor {

    convenience init(r: UInt8, g: UInt8, b: UInt8, alpha: CGFloat = 1.0) {
        let divider: CGFloat = 255.0
        self.init(red: CGFloat(r)/divider, green: CGFloat(g)/divider, blue: CGFloat(b)/divider, alpha: alpha)
    }

    private convenience init(rgbWithoutValidation value: Int32, alpha: CGFloat = 1.0) {
        self.init(
            r: UInt8((value & 0xFF0000) >> 16),
            g: UInt8((value & 0x00FF00) >> 8),
            b: UInt8(value & 0x0000FF),
            alpha: alpha
        )
    }

    convenience init?(rgb: Int32, alpha: CGFloat = 1.0) {
        if rgb > 0xFFFFFF || rgb < 0 { return nil }
        self.init(rgbWithoutValidation: rgb, alpha: alpha)
    }

    convenience init?(hex: String, alpha: CGFloat = 1.0) {
        var charSet = CharacterSet.whitespacesAndNewlines
        charSet.insert("#")
        let _hex = hex.trimmingCharacters(in: charSet)
        guard _hex.range(of: "^[0-9A-Fa-f]{6}$", options: .regularExpression) != nil else { return nil }
        var rgb: UInt32 = 0
        Scanner(string: _hex).scanHexInt32(&rgb)
        self.init(rgbWithoutValidation: Int32(rgb), alpha: alpha)
    }
}

使用

let alpha: CGFloat = 1.0

// Hex
print(UIColor(rgb: 0x4F9BF5) ?? "nil")
print(UIColor(rgb: 0x4F9BF5, alpha: alpha) ?? "nil")
print(UIColor(rgb: 5217269) ?? "nil")
print(UIColor(rgb: -5217269) ?? "nil")                  // = nil
print(UIColor(rgb: 0xFFFFFF1) ?? "nil")                 // = nil

// String
print(UIColor(hex: "4F9BF5") ?? "nil")
print(UIColor(hex: "4F9BF5", alpha: alpha) ?? "nil")
print(UIColor(hex: "#4F9BF5") ?? "nil")
print(UIColor(hex: "#4F9BF5", alpha: alpha) ?? "nil")
print(UIColor(hex: "#4F9BF56") ?? "nil")                // = nil
print(UIColor(hex: "#blabla") ?? "nil")                 // = nil

// RGB
print(UIColor(r: 79, g: 155, b: 245))
print(UIColor(r: 79, g: 155, b: 245, alpha: alpha))
//print(UIColor(r: 792, g: 155, b: 245, alpha: alpha))  // Compiler will throw an error, r,g,b = [0...255]

你可以在swift 5中使用它

斯威夫特5

import UIKit

extension UIColor {
    static func hexStringToUIColor (hex:String) -> UIColor {
        var cString:String = hex.trimmingCharacters(in: .whitespacesAndNewlines).uppercased()

        if (cString.hasPrefix("#")) {
            cString.remove(at: cString.startIndex)
        }

        if ((cString.count) != 6) {
            return UIColor.gray
        }

        var rgbValue:UInt32 = 0
        Scanner(string: cString).scanHexInt32(&rgbValue)

        return UIColor(
            red: CGFloat((rgbValue & 0xFF0000) >> 16) / 255.0,
            green: CGFloat((rgbValue & 0x00FF00) >> 8) / 255.0,
            blue: CGFloat(rgbValue & 0x0000FF) / 255.0,
            alpha: CGFloat(1.0)
        )
    }
}

Swift 5.3 & SwiftUI:通过UIColor支持十六进制和CSS颜色名称

依据代码

斯威夫特包

SwiftUI包

字符串的例子:

橙子、酸橙、番茄等。 Clear, Transparent, nil和空字符串产生[UIColor clearColor] 美国广播公司 abc7 # abc7 00飞行符 # 00飞行符 00 ffff77

操场上的输出:

iOS 14, SwiftUI 2.0, swift 5.1, Xcode beta12

extension Color {
  static func hexColour(hexValue:UInt32)->Color
    {
      let red = Double((hexValue & 0xFF0000) >> 16) / 255.0
      let green = Double((hexValue & 0xFF00) >> 8) / 255.0
      let blue = Double(hexValue & 0xFF) / 255.0
      return Color(red:red, green:green, blue:blue)
    }
}

用十六进制数表示

let red = Color.hexColour(hexValue: 0xFF0000)

用户界面颜色:

extension UIColor {

    convenience init(hex: Int) {
        let components = (
            R: CGFloat((hex >> 16) & 0xff) / 255,
            G: CGFloat((hex >> 08) & 0xff) / 255,
            B: CGFloat((hex >> 00) & 0xff) / 255
        )
        self.init(red: components.R, green: components.G, blue: components.B, alpha: 1)
    }

}

CGColor:

extension CGColor {

    class func colorWithHex(hex: Int) -> CGColorRef {

        return UIColor(hex: hex).CGColor

    }

}

使用

let purple = UIColor(hex: 0xAB47BC)