UITableViewController with a fixed bottom button

UITableViewController+FixBottomBar.swift

class MyTableViewController: UITableViewController {
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        bottomButton.size = CGSize(width: self.view.width, height: 50)
        bottomButton.translatesAutoresizingMaskIntoConstraints = false
        bottomButton.addTarget(self, action: #selector(bottomButtonClick), for: .touchUpInside)

        self.navigationController?.setToolbarHidden(false, animated: animated)
        let btn = UIBarButtonItem(title: "", style: .plain, target: self, action: #selector(bottomButtonClick))
        let fixspace = UIBarButtonItem(barButtonSystemItem: .fixedSpace, target: nil, action: nil)
        fixspace.width = CGFloat.leastNormalMagnitude
        self.navigationController?.toolbar.items = [fixspace, btn, fixspace]

        self.navigationController?.toolbar.addSubview(bottomButton)
        self.navigationController?.toolbar.leadingAnchor.constraint(equalTo: bottomButton.leadingAnchor).isActive = true
        self.navigationController?.toolbar.trailingAnchor.constraint(equalTo: bottomButton.trailingAnchor).isActive = true
        self.navigationController?.toolbar.topAnchor.constraint(equalTo: bottomButton.topAnchor).isActive = true
        self.navigationController?.toolbar.bottomAnchor.constraint(equalTo: bottomButton.bottomAnchor).isActive = true
        self.navigationController?.toolbar.clipsToBounds = true
    }
    
    @objc private func bottomButtonClick() {

    }
    
}