UILabel extension for truncated state

UILabel+Truncate.swift

//
//  UILabel+Extension.swift
//  ShopAdvisor
//
//  Created by Christian Ascone on 21/06/2017.
//  Copyright © 2017 Luna srls. All rights reserved.
//

import Foundation

extension UILabel {
    /// Check if this uilabel has been truncated
    ///
    /// - Returns: true if label has been truncated, false otherwise
    func isTruncated() -> Bool {
        
        if let string = self.text {
            
            let size: CGSize = (string as NSString).boundingRect(
                with: CGSize(width: self.frame.size.width, height: CGFloat.greatestFiniteMagnitude),
                options: NSStringDrawingOptions.usesLineFragmentOrigin,
                attributes: [NSFontAttributeName: self.font],
                context: nil).size
            
            return (size.height > self.bounds.size.height)
        }
        
        return false
    }
    
    
    /// Gets length of visible text of this uilabel
    ///
    /// - Returns: characters count of visible characters
    func visibleTextLength() -> Int {
        let font: UIFont = self.font
        let mode: NSLineBreakMode = self.lineBreakMode
        let labelWidth: CGFloat = self.frame.size.width
        let labelHeight: CGFloat = self.frame.size.height
        let sizeConstraint = CGSize(width: labelWidth, height: CGFloat.greatestFiniteMagnitude)
        
        let attributes: [AnyHashable: Any] = [NSFontAttributeName: font]
        let attributedText = NSAttributedString(string: self.text!, attributes: attributes as? [String : Any])
        let boundingRect: CGRect = attributedText.boundingRect(with: sizeConstraint, options: .usesLineFragmentOrigin, context: nil)
        
        if boundingRect.size.height > labelHeight {
            var index: Int = 0
            var prev: Int = 0
            let characterSet = CharacterSet.whitespacesAndNewlines
            repeat {
                prev = index
                if mode == NSLineBreakMode.byCharWrapping {
                    index += 1
                } else {
                    index = (self.text! as NSString).rangeOfCharacter(from: characterSet, options: [], range: NSRange(location: index + 1, length: self.text!.characters.count - index - 1)).location
                }
            } while index != NSNotFound && index < self.text!.characters.count && (self.text! as NSString).substring(to: index).boundingRect(with: sizeConstraint, options: .usesLineFragmentOrigin, attributes: attributes as? [String : Any], context: nil).size.height <= labelHeight
            return prev
        }
        return self.text!.characters.count
    }
}