I tried to use NSMutableAttributedString to show a reach text in UILabel, but I've found it's hard to got a method to find out the range of the-string inside of a string. Here is what that I've done.hope this helped you!
let attrString = NSMutableAttributedString(string:desc)
if let strRange = desc.rangeOfString(stringInSearchBar){
let distanceBegin = distance(desc.startIndex, strRange.startIndex)
let distanceEnd = distance(desc.startIndex, strRange.endIndex)
let range = NSMakeRange(distanceBegin, distanceEnd - distanceBegin)
attrString.addAttribute(NSForegroundColorAttributeName, value: UIColor.markColorRed(), range:range)
}