Number of text lines in UITextView

UITextView+Lines.swift

extension NSLayoutManager {
    var numberOfLines: Int {
        var linesCount: Int = 0
        var idx: Int = 0
        let lineRange: NSRangePointer = .allocate(capacity: 1)
        while idx < numberOfGlyphs {
            lineFragmentRect(forGlyphAt: idx, effectiveRange: lineRange)
            idx = NSMaxRange(lineRange.pointee)
            linesCount += 1
        }
        lineRange.deallocate()
        return linesCount
    }
}

extension UITextView {
    var numberOfLines: Int {
        layoutManager.numberOfLines
    }
}

based on: https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/TextLayout/Tasks/CountLines.html