(iOS) Label string highlight

UILabel+highlight.swift

import UIKit
extension UILabel {

    /// Highlights a specific substring of the label's text with a desired color
    /// Text must be set before calling this method.
    ///
    /// - Parameters:
    ///   - subString: The substring to change color
    ///   - color: The desired color
    func highlight(subString: String, color: UIColor?) {
        guard let text = self.text,
              let color = color else {
            return
        }
        let attributedString = NSMutableAttributedString(string: text)
        let option = NSString.CompareOptions.caseInsensitive
        let range = attributedString.mutableString.range(of: subString,
                                                         options: option)
        if range.location != NSNotFound {
            attributedString.beginEditing()
            attributedString.addAttribute(NSAttributedString.Key.foregroundColor,
                                          value: color,
                                          range: range)
            attributedString.endEditing()
            self.attributedText = attributedString
        }
        self.layoutIfNeeded()
    }

    /// Resets the highlighting to the previous font style
    func resetHighlighting() {
        guard let text = self.text,
              let textColor = self.fontColor else {
            return
        }

        let attributedString = NSMutableAttributedString(string: text)
        let option = NSString.CompareOptions.caseInsensitive
        let range = attributedString.mutableString.range(of: text,
                                                         options: option)
        if range.location != NSNotFound {
            attributedString.beginEditing()
            attributedString.addAttribute(NSAttributedString.Key.foregroundColor,
                                          value: textColor,
                                          range: range)
            attributedString.endEditing()
            self.attributedText = attributedString
        }
        self.layoutIfNeeded()
    }
}