How to find actual number of lines of UILabel?

Question

How can I find the actual number of lines of a UILabel after I have initialized it with a text and a font? I have set its numberOfLines property to 0, so it will expand to however many lines are necessary. But then, how can I find out how many lines it finally got after I set its text?

I found similar questions, but none seems to provide a concise answer and it seems to me that it must be really easy to get it without any overhead on juggling around with the boundingRectWithSize or sizeWithFont,...

Answer 1

None of these worked for me. Below one did,

Swift 4.2:

extension UILabel {
    func calculateMaxLines() -> Int {
        let maxSize = CGSize(width: frame.size.width, height: CGFloat(Float.infinity))
        let charSize = font.lineHeight
        let text = (self.text ?? "") as NSString
        let textSize = text.boundingRect(with: maxSize, options: .usesLineFragmentOrigin, attributes: [NSAttributedString.Key.font: font], context: nil)
        let linesRoundedUp = Int(ceil(textSize.height/charSize)) 
        return linesRoundedUp
    }    
}

Swift 4/4.1:

extension UILabel {

    func calculateMaxLines() -> Int {
        let maxSize = CGSize(width: frame.size.width, height: CGFloat(Float.infinity))
        let charSize = font.lineHeight
        let text = (self.text ?? "") as NSString
        let textSize = text.boundingRect(with: maxSize, options: .usesLineFragmentOrigin, attributes: [.font: font], context: nil)
        let linesRoundedUp = Int(ceil(textSize.height/charSize)) 
        return linesRoundedUp
    }

}

Swift 3:

extension UILabel {

    func calculateMaxLines() -> Int {
        let maxSize = CGSize(width: frame.size.width, height: CGFloat(Float.infinity))
        let charSize = font.lineHeight
        let text = (self.text ?? "") as NSString
        let textSize = text.boundingRect(with: maxSize, options: .usesLineFragmentOrigin, attributes: [NSFontAttributeName: font], context: nil)
        let linesRoundedUp = Int(ceil(textSize.height/charSize)) 
        return linesRoundedUp
    }

}