UIColor扩展—Swift

extension UIColor {
convenience init(bd_hexColor hexValue: String) {
var red: CGFloat = 0.0
var green: CGFloat = 0.0
var blue: CGFloat = 0.0
var alpha: CGFloat = 1.0

var hexColorString = hexValue;

    if !hexColorString.hasPrefix("#"){
        hexColorString = "#"+hexValue;
    }

    let index   = hexColorString.startIndex.advancedBy(1)
    let hex     = hexColorString.substringFromIndex(index)
    let scanner = NSScanner(string: hex)
    var hexValue: CUnsignedLongLong = 0
    if scanner.scanHexLongLong(&hexValue) {
        switch (hex.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:
            red   = CGFloat((hexValue & 0xFF000000) >> 24) / 255.0
            green = CGFloat((hexValue & 0x00FF0000) >> 16) / 255.0
            blue  = CGFloat((hexValue & 0x0000FF00) >> 8)  / 255.0
            alpha = CGFloat(hexValue & 0x000000FF)         / 255.0
        default:
            BMLog("Invalid RGB string,number of characters after '#' should be either 3,4,6 or 8")
        }
    } else {
        BMLog("Scan hex error")
    }
    self.init(red:red,green:green,blue:blue,alpha:alpha)
}

}