CustomCell

protocol HeightForTextView {
    func heightOfTextView(height: CGFloat)
}

class CommentCell:UITableViewCell {

 var delegate:HeightForTextView?

 override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
        super.init(style: style, reuseIdentifier: reuseIdentifier)
        textViewContstraints()
        
    }
    
    func textViewDidChange(textView: UITextView) {
        var fixedWidth: CGFloat = textView.frame.size.width
        var newSize: CGSize = textView.sizeThatFits(CGSize(width: fixedWidth, height: CGFloat.greatestFiniteMagnitude))

        if let iuDelegate = self.delegate {
            print("delegate text view")
            iuDelegate.heightOfTextView(height: newSize.height)
        }


    }

  func textViewContstraints() {
        textView.translatesAutoresizingMaskIntoConstraints = false
        var frame = self.textView.frame
        frame.size.height = self.textView.contentSize.height
        self.textView.frame = frame
        textViewDidChange(textView: self.textView)
        
    }
}

ViewController

class CommentVC: UIViewController, UITableViewDelegate, UITableViewDataSource, UITextFieldDelegate, HeightForTextView {  
    func heightOfTextView(height: CGFloat) {
        textViewHeight = height
        self.myTableView.beginUpdates()
        self.myTableView.endUpdates()
    }
    
   var textViewHeight = CGFloat()

func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
       return textViewHeight + 70
    }

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = myTableView.dequeueReusableCell(withIdentifier: "MyCell", for: indexPath as IndexPath) as! CommentCell
        cell.delegate = self
        
        return cell
    }
}