MarcoMig

//ClassA it's the owner of the callback, he will trigger the callback when it's the time
class ClassA {
    //The property of that will be associated to the ClassB callback
    var callbackBlock : ((error : NSError?, message : String?, adress : String? ) -> Void)?
    
    init() {
        //Do Your staff
    }
    
    //Define your function with the clousure as a parameter

MarcoMig

// Creates a UIColor from a Hex string.
func colorWithHexString (hex:String) -> UIColor {
  var cString:String = hex.stringByTrimmingCharactersInSet(NSCharacterSet.whitespaceAndNewlineCharacterSet()).uppercaseString
  
  if (cString.hasPrefix("#")) {
    cString = cString.substringFromIndex(1)
  }
  
  if (countElements(cString) != 6) {
    return UIColor.grayColor()