Get height of text block with given width and font

StringExt.swift

extension String {
  func heightWithConstrainedWidth(width: CGFloat, font: UIFont) -> CGFloat {
    let constraintRect = CGSize(width: width, height: CGFloat.max)
    
    let boundingBox = self.boundingRectWithSize(constraintRect, options: NSStringDrawingOptions.UsesLineFragmentOrigin, attributes: [NSFontAttributeName: font], context: nil)
    
    return boundingBox.height
  }
  
  func isEmail() -> Bool {
    let regex = try? NSRegularExpression(pattern: "^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$", options: .CaseInsensitive)
    return regex?.firstMatchInString(self, options: [], range: NSMakeRange(0, self.characters.count)) != nil
  }
}