You Can Get UIColor From String Code Like
   circularSpinner.fillColor = [self getUIColorObjectFromHexString:@"27b8c8" alpha:9];

 //Function For Hex Color Use
    - (unsigned int)intFromHexString:(NSString *)hexStr
    {
        unsigned int hexInt = 0;

        // Create scanner
        NSScanner *scanner = [NSScanner scannerWithString:hexStr];

        // Tell scanner to skip the # character
        [scanner setCharactersToBeSkipped:[NSCharacterSet characterSetWithCharactersInString:@"#"]];

        // Scan hex value
        [scanner scanHexInt:&hexInt];

        return hexInt;
    }




    - (UIColor *)getUIColorObjectFromHexString:(NSString *)hexStr alpha:(CGFloat)alpha
    {
        // Convert hex string to an integer
        unsigned int hexint = [self intFromHexString:hexStr];

        // Create color object, specifying alpha as well
        UIColor *color =
        [UIColor colorWithRed:((CGFloat) ((hexint & 0xFF0000) >> 16))/255
                        green:((CGFloat) ((hexint & 0xFF00) >> 8))/255
                         blue:((CGFloat) (hexint & 0xFF))/255
                        alpha:alpha];

        return color;
    }

    /Function For Hex Color Use
    - (unsigned int)intFromHexString:(NSString *)hexStr
    {
        unsigned int hexInt = 0;

        // Create scanner
        NSScanner *scanner = [NSScanner scannerWithString:hexStr];

        // Tell scanner to skip the # character
        [scanner setCharactersToBeSkipped:[NSCharacterSet characterSetWithCharactersInString:@"#"]];

        // Scan hex value
        [scanner scanHexInt:&hexInt];

        return hexInt;
    }




    - (UIColor *)getUIColorObjectFromHexString:(NSString *)hexStr alpha:(CGFloat)alpha
    {
        // Convert hex string to an integer
        unsigned int hexint = [self intFromHexString:hexStr];

        // Create color object, specifying alpha as well
        UIColor *color =
        [UIColor colorWithRed:((CGFloat) ((hexint & 0xFF0000) >> 16))/255
                        green:((CGFloat) ((hexint & 0xFF00) >> 8))/255
                         blue:((CGFloat) (hexint & 0xFF))/255
                        alpha:alpha];

        return color;
    }

另一个带有alpha的版本

#define UIColorFromRGBA(rgbValue) [UIColor colorWithRed:((float)((rgbValue & 0xFF000000) >> 24))/255.0 green:((float)((rgbValue & 0xFF0000) >> 16))/255.0 blue:((float)((rgbValue & 0xFF00) >> 8 ))/255.0 alpha:((float)((rgbValue & 0xFF))/255.0)]

extension UIColor {
    convenience init(hexaString: String, alpha: CGFloat = 1) {
        let chars = Array(hexaString.dropFirst())
        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)}
}

用法:

let redColor       = UIColor(hexaString: "#FF0000")              // r 1,0 g 0,0 b 0,0 a 1,0
let transparentRed = UIColor(hexaString: "#FF0000", alpha: 0.5)  // r 1,0 g 0,0 b 0,0 a 0,5

另一种选择是将六值转换为无符号整数，并从中提取相应的值:

extension UIColor {
    convenience init(hexaString: String, alpha: CGFloat = 1) {
        self.init(hexa: UInt(hexaString.dropFirst(), radix: 16) ?? 0, alpha: alpha)
    }
    convenience init(hexa: UInt, alpha: CGFloat = 1) {
        self.init(red:   .init((hexa & 0xff0000) >> 16) / 255,
                  green: .init((hexa & 0xff00  ) >>  8) / 255,
                  blue:  .init( hexa & 0xff    )        / 255,
                  alpha: alpha)
    }
}

let purpleColor       = UIColor(hexaString: "#FF00FF")    // r 1,0 g 0,0 b 1,0 a 1,0
let transparentYellow = UIColor(hexaString: "#FFFF00", alpha: 0.5)  // r 1,0 g 1,0 b 0,0 a 0,5

伊森·斯特里德回答的简单例子。一个接受十六进制字符串并返回UIColor的函数。 (你可以输入十六进制字符串格式:#ffffff或ffffff)

例子:

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

    if (cString.hasPrefix("#")) {
        if let range = cString.range(of: cString) {
            cString = cString.substring(from: cString.index(range.lowerBound, offsetBy: 1))
        }
    }

    if ((cString.characters.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)
    )
}

用法:

var color1 = hexStringToUIColor("#d3d3d3")

张贴参考网站我刚刚找到。 它做了所有的脏工作，从HEX或RGB开始，在ObjC, Swift和Xamarin中打印出代码。

https://www.uicolor.xyz/#/hex-to-ui

你可以做这样的扩展

extension UIColor {
    convenience init(hex: UInt, alpha: CGFloat = 1) {
        self.init(
            red: CGFloat((hex & 0xFF0000) >> 16) / 255.0,
            green: CGFloat((hex & 0x00FF00) >> 8) / 255.0,
            blue: CGFloat(hex & 0x0000FF) / 255.0,
            alpha: alpha
        )
    }
}

像这样用在任何地方

let color1 = UIColor(hex: 0xffffff)
let color2 = UIColor(hex: 0xffffff, alpha: 0.2)