Swift 2.0
Вот пример:
let newsString: NSMutableAttributedString = NSMutableAttributedString(string: "Tap here to read the latest Football News.")
newsString.addAttributes([NSUnderlineStyleAttributeName: NSUnderlineStyle.StyleDouble.rawValue], range: NSMakeRange(4, 4))
sampleLabel.attributedText = newsString.copy() as? NSAttributedString
OR
let stringAttributes = [
NSFontAttributeName : UIFont(name: "Helvetica Neue", size: 17.0)!,
NSUnderlineStyleAttributeName : 1,
NSForegroundColorAttributeName : UIColor.orangeColor(),
NSTextEffectAttributeName : NSTextEffectLetterpressStyle,
NSStrokeWidthAttributeName : 2.0]
let atrributedString = NSAttributedString(string: "Sample String: Attributed", attributes: stringAttributes)
sampleLabel.attributedText = atrributedString