Autoresizing text view

TextView.swift

import UIKit

public final class TextView: UITextView {
  
  public override init(frame: CGRect, textContainer: NSTextContainer?) {
    super.init(frame: frame, textContainer: textContainer)
    layoutManager.delegate = self
    isScrollEnabled = false
  }
  
  @available(*, unavailable)
  required init?(coder: NSCoder) { fatalError() }
  
  public override var intrinsicContentSize: CGSize {
    sizeThatFits(CGSize(width: bounds.width, height: .greatestFiniteMagnitude))
  }
  
  public var numberOfLines: Int {
    var linesCount: Int = 0
    var idx: Int = 0
    let lineRange: NSRangePointer = .allocate(capacity: 1)
    while idx < layoutManager.numberOfGlyphs {
      layoutManager.lineFragmentRect(forGlyphAt: idx, effectiveRange: lineRange)
      idx = NSMaxRange(lineRange.pointee)
      linesCount += 1
    }
    lineRange.deallocate()
    return linesCount
  }
}

extension TextView: NSLayoutManagerDelegate {
    public func layoutManagerDidInvalidateLayout(_ sender: NSLayoutManager) {
        invalidateIntrinsicContentSize()
    }
}