SelfSizingCollectionViewCellDemo+UITextView.swift

//
//  ViewController.swift
//  CVSelfSizingCells
//
//  Created by Jolas L on 13/06/20.
//  Copyright © 2020 Jolas L. All rights reserved.
//

import UIKit

class ViewController: UIViewController, UICollectionViewDataSource {
    
    let collectionView: UICollectionView = {
        let flowLayout = UICollectionViewFlowLayout()
        flowLayout.estimatedItemSize = UICollectionViewFlowLayout.automaticSize
        let collectionView = UICollectionView(frame: .zero, collectionViewLayout: flowLayout)
        collectionView.translatesAutoresizingMaskIntoConstraints = false
        return collectionView
    }()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        view.addSubview(collectionView)
        collectionView.dataSource = self
        collectionView.backgroundColor = .white
        collectionView.register(MultiLineCell.self, forCellWithReuseIdentifier: "cellId")
        
        NSLayoutConstraint.activate([
            collectionView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            collectionView.topAnchor.constraint(equalTo: view.topAnchor),
            collectionView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            collectionView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
        ])
    }
    
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        dummyTextMessages.count
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cellId", for: indexPath) as! MultiLineCell
        cell.textView.text = dummyTextMessages[indexPath.row]
        cell.maxWidth = collectionView.frame.width
        return cell
    }
}

class MultiLineCell: UICollectionViewCell{
    let containerView: UIView = {
        let view = UIView()
        view.translatesAutoresizingMaskIntoConstraints = false
        return view
    }()
    
    let textView: UITextView = {
        let textView = UITextView()
        textView.backgroundColor = .red
        textView.font = UIFont.systemFont(ofSize: 20)
        textView.isScrollEnabled = false
        textView.translatesAutoresizingMaskIntoConstraints = false
        return textView
    }()
    
    private var containerViewWidthAnchor:NSLayoutConstraint!
    private var textViewHeightContraint: NSLayoutConstraint!
    var maxWidth: CGFloat? {
        didSet {
            guard let maxWidth = maxWidth else {
                return
            }
            containerViewWidthAnchor.constant = maxWidth
            containerViewWidthAnchor.isActive = true
            
            let sizeToFitIn = CGSize(width: maxWidth, height: CGFloat(MAXFLOAT))
            let newSize = self.textView.sizeThatFits(sizeToFitIn)
            self.textViewHeightContraint.constant = newSize.height
        }
    }
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        backgroundColor = .cyan
        contentView.addSubview(containerView)
        containerView.addSubview(textView)
        
        textViewHeightContraint = textView.heightAnchor.constraint(equalToConstant: 0)
        containerViewWidthAnchor = containerView.widthAnchor.constraint(equalToConstant: 0)
        
        NSLayoutConstraint.activate([
            containerView.leadingAnchor.constraint(equalTo: contentView.leadingAnchor),
            containerView.topAnchor.constraint(equalTo: contentView.topAnchor),
            containerView.trailingAnchor.constraint(equalTo: contentView.trailingAnchor),
            containerView.bottomAnchor.constraint(equalTo: contentView.bottomAnchor),
            
            textView.leadingAnchor.constraint(equalTo: containerView.leadingAnchor),
            textView.topAnchor.constraint(equalTo: containerView.topAnchor),
            textView.trailingAnchor.constraint(equalTo: containerView.trailingAnchor),
            textView.bottomAnchor.constraint(equalTo: containerView.bottomAnchor),
        ])
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

let dummyTextMessages = [
    "Hello",
    "Hi",
    "Hey! Last time I have purchased a brand new watch from  solutions.",
    "Thanks for contacting us  we are here to help you. Please read all the schemes. ",
    "Sathish Kumar V Thanks for reaching out. Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambprinter took a galley Hgjhagsdg asjhdgjhasgdjha asjhdgajhsdghjasg asjhdgjhagsd jhagsdjhgasjhdgajsd",
    "Hel asdjjha skjhajsdhalo",
    "H jkahskdhaksdh jkahsgdjh jahsgh hgashdgh hhh hghg hghsgdhgash ello",
    "kjjkasjkdjk jaskjdjkasdjk  askjjkaskjkjkjskj nskjkskik s k skksknn",
    "aslkdjkjas ajksdkjasd ajksdkjasd",
    "askjdjkasdjkasd",
]

This piece of code does not work in Swift 5, Xcode 12.5