NSAttributedString+Highlight

NSAttributedStringHighlight.swift

extension NSAttributedString {
    func highlighting(_ substring: String, using color: UIColor) -> NSAttributedString {
        let attributedString = NSMutableAttributedString(attributedString: self)
        attributedString.addAttribute(.foregroundColor, value: color, range: (self.string as NSString).range(of: substring))
        return attributedString
    }
}

// Usage:

label.attributedText = NSAttributedString(string: "Budapest")
label.attributedText = label.attributedText?.highlighting("Bud", using: .blue)