ViewController.swift

import UIKit
import Parchment

class FirstVC: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        self.title = "First"
        self.view.backgroundColor = .red
    }
}

class SecondVC: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        self.title = "Second"
        self.view.backgroundColor = .blue
    }
}

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        
        let firstVC = FirstVC()
        firstVC.title = "asd"
        let secondVC = SecondVC()
        secondVC.title = "asd"
        
        let pagingViewController = FixedPagingViewController(viewControllers: [firstVC, secondVC])
        pagingViewController.menuItemSize = .sizeToFit(minWidth: 120, height: 50) // I had to gave a menuItemSize value if I didn't menuItem would be collapsed.
        addChildViewController(pagingViewController)
        view.addSubview(pagingViewController.view)
        pagingViewController.didMove(toParentViewController: self)

        pagingViewController.view.translatesAutoresizingMaskIntoConstraints = false
        
        NSLayoutConstraint.activate([
            pagingViewController.view.topAnchor.constraint(equalTo: view.topAnchor),
            pagingViewController.view.bottomAnchor.constraint(equalTo: view.bottomAnchor),
            pagingViewController.view.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            pagingViewController.view.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            ])
    }

}