Converting from hex to UIColor

UIColor+fromHexString.swift

extension UIColor {
    static func from(hex: String) -> UIColor? {
        assert(hex.characters.first! == "#", "Maybe not a valid colour \(hex)")
        var val = hex.substringFromIndex(hex.startIndex.advancedBy(1))
        switch val.characters.count {
        case 3: val.appendContentsOf("f"); fallthrough
        case 4: val = val.characters.map{"\($0)\($0)"}.joinWithSeparator("")
        case 6: val.appendContentsOf("ff")
        case 8: do {}
        default: return nil // not proper format: #rgb, #rgba, #rrggbb, #rrggbbaa
        }
        if let hexColor = Int64.init(val, radix: 16) {
            let r = CGFloat((hexColor & 0xFF000000) >> 24) / 255.0
            let g = CGFloat((hexColor & 0x00FF0000) >> 16) / 255.0
            let b = CGFloat((hexColor & 0x0000FF00) >> 08) / 255.0
            let a = CGFloat((hexColor & 0x000000FF) >> 00) / 255.0
            
            return UIColor(red: r, green: g, blue: b, alpha: a)
        } else {
            return nil
        }
    }
}

print(UIColor.from("#F00")!)       // UIDeviceRGBColorSpace 1 0 0 1
print(UIColor.from("#0F0")!)       // UIDeviceRGBColorSpace 0 1 0 1
print(UIColor.from("#00F")!)       // UIDeviceRGBColorSpace 0 0 1 1
print(UIColor.from("#FF0000")!)    // UIDeviceRGBColorSpace 1 0 0 1
print(UIColor.from("#00FF00")!)    // UIDeviceRGBColorSpace 0 1 0 1
print(UIColor.from("#0000FF")!)    // UIDeviceRGBColorSpace 0 0 1 1
print(UIColor.from("#FF000000")!)  // UIDeviceRGBColorSpace 1 0 0 0
print(UIColor.from("#00FF0000")!)  // UIDeviceRGBColorSpace 0 1 0 0
print(UIColor.from("#0000FF00")!)  // UIDeviceRGBColorSpace 0 0 1 0
print(UIColor.from("#000000FF")!)  // UIDeviceRGBColorSpace 0 0 0 1