Apple Journal Calendar UI Demo

ViewController.swift

//
//  ViewController.swift
//  Journal-Calendar-Demo
//
//  Created by Seb Vidal on 30/04/2024.
//

import UIKit

class ViewController: UIViewController {
    // MARK: - init(nibName:bundle:)
    override init(nibName: String?, bundle: Bundle?) {
        super.init(nibName: nibName, bundle: bundle)
        
        let button = UIButton(type: .system)
        button.setTitle("Show Calendar", for: .normal)
        button.translatesAutoresizingMaskIntoConstraints = false
        button.addTarget(self, action: #selector(showAlertController), for: .touchUpInside)
        
        view.addSubview(button)
        
        NSLayoutConstraint.activate([
            button.centerXAnchor.constraint(equalTo: view.centerXAnchor),
            button.centerYAnchor.constraint(equalTo: view.centerYAnchor)
        ])
    }
    
    // MARK: - init(coder:)
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    // MARK: - Private Methods
    @objc private func showAlertController(_ sender: UIButton) {
        let selector = NSSelectorFromString("_setHeaderContentViewController:")
        let headerContentViewController = CalendarViewController()
        
        let alertController = UIAlertController(title: nil, message: nil, preferredStyle: .actionSheet)
        alertController.perform(selector, with: headerContentViewController)
        alertController.addAction(UIAlertAction(title: "Cancel", style: .cancel) { _ in})
        
        present(alertController, animated: true)
    }
}

class CalendarViewController: UIViewController {
    // MARK: - Private Properties
    private var calendarView: UICalendarView!
    
    // MARK: - init(nibName:bundle:)
    override init(nibName: String?, bundle: Bundle?) {
        super.init(nibName: nibName, bundle: bundle)
        
        calendarView = UICalendarView()
        calendarView.translatesAutoresizingMaskIntoConstraints = false
        
        view.addSubview(calendarView)
        
        NSLayoutConstraint.activate([
            calendarView.topAnchor.constraint(equalTo: view.topAnchor),
            calendarView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            calendarView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            calendarView.bottomAnchor.constraint(equalTo: view.bottomAnchor)
        ])
    }
    
    // MARK: - init(coder:)
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    // MARK: - viewDidLayoutSubviews()
    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        let height = calendarView.intrinsicContentSize.height
        preferredContentSize = CGSize(width: -1, height: height)
    }
}