UIColorFromRGB - adapted from http://stackoverflow.com/a/12397366 for Swift

UIColorFromRGB.swift

/**
Returns a UIColor object from a Hexadecimal string with a solid colour

i.e. 

UIColorFromRGB("#FF0000") == UIColor.redColor()
UIColorFromRGB("#0000FF") == UIColor.blueColor()
UIColorFromRGB("#GGGGGG") == UIColor.blackColor()
UIColorFromRGB("#Hello") == UIColor.blackColor()

Adapted from http://stackoverflow.com/a/12397366

:param: color The hexadecimal string representation of the string including the #
:returns: a UIColor, UIColor.blackColor() if the casting fails
*/
func UIColorFromRGB(color: String) -> UIColor {
    return UIColorFromRGB(color, 1.0)
}

/**
Returns a UIColor object from a Hexadecimal string with an adjustable alpha channel

i.e.
UIColorFromRGB("#FF0000", 1.0) == UIColor.redColor()
UIColorFromRGB("#0000FF", 1.0) == UIColor.blueColor()
UIColorFromRGB("#GGGGGG", 1.0) == UIColor.blackColor()
UIColorFromRGB("#Hello", 1.0) == UIColor.blackColor()

Adapted from http://stackoverflow.com/a/12397366

:param: color The hexadecimal string representation of the string including the #
:param: alpha The transparency, represented as a Double between 0 and 1
:returns: a UIColor, UIColor.blackColor() if the casting fails
*/
func UIColorFromRGB(color: String, alpha: Double) -> UIColor {
    assert(alpha <= 1.0, "The alpha channel cannot be above 1")
    assert(alpha >= 0, "The alpha channel cannot be below 0")
    var rgbValue : UInt32 = 0
    let scanner = NSScanner(string: color)
    scanner.scanLocation = 1
    
    if scanner.scanHexInt(&rgbValue) {
        let red = CGFloat((rgbValue & 0xFF0000) >> 16) / 255.0
        let green = CGFloat((rgbValue & 0xFF00) >> 8) / 255.0
        let blue = CGFloat(rgbValue & 0xFF) / 255.0
        
        return UIColor(red: red, green: green, blue: blue, alpha: CGFloat(alpha))
    }
    
    return UIColor.blackColor()
}