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How to convert a hex color to a UIColor

Paul Hudson       @twostraws

Here's a simple extension to UIColor that lets you create colors from hex strings. The new method is a failable initializer, which means it returns nil if you don't specify a color in the correct format. It should be a # symbol, followed by red, green, blue and alpha in hex format, for a total of nine characters. For example, #ffe700ff is gold.

Here's the code:

extension UIColor {
    public convenience init?(hexString: String) {
        let r, g, b, a: CGFloat

        if hexString.hasPrefix("#") {
            let start = hexString.index(hexString.startIndex, offsetBy: 1)
            let hexColor = String(hexString[start...])

            if hexColor.count == 8 {
                let scanner = Scanner(string: hexColor)
                var hexNumber: UInt64 = 0

                if scanner.scanHexInt64(&hexNumber) {
                    r = CGFloat((hexNumber & 0xff000000) >> 24) / 255
                    g = CGFloat((hexNumber & 0x00ff0000) >> 16) / 255
                    b = CGFloat((hexNumber & 0x0000ff00) >> 8) / 255
                    a = CGFloat(hexNumber & 0x000000ff) / 255

                    self.init(red: r, green: g, blue: b, alpha: a)
                    return
                }
            }
        }

        return nil
    }
}

If you wanted it always to return a value, change init? to be init then change the return nil line at the end to be return UIColor.black or whatever you'd like the default value to be.

To use the extension, write code like this:

let gold = UIColor(hexString: "#ffe700ff")

Available from iOS 2.0

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