How to disable the new UITabBarController view style in iPadOS 18

iPadOS 18 introduces new API for creating tab bars.

Create a UITabBarController and assign an array of UITab objects to its tabs property.

How do we disable this new style and keep the tab bar at the bottom for iPadOS 18?

After playing around, I have found the following to work the best. It works with split screen resizing, the more tab, keeps the original Tab Bar on iPhones and older iOS, adjusts layout margins for child view controllers, and can still compile under Xcode 15.

Basically it just hides the new tab bar and places the old style back, copying the tab bar items and selected item across.

class CustomTabBarController: UITabBarController {

    /// Active for iPads running iOS 18+ where the traditional tab bar has been removed by Apple
    lazy var alternateTabBarActive: Bool = {
    #if compiler(>=6.0) // Compiler flag for Xcode >= 16
        if #available(iOS 18.0, *), UIDevice.current.userInterfaceIdiom == .pad {
            self.isTabBarHidden = true
            return true
        }
    #endif
        return false
    }()
    
    var tabBarHeightConstraint: NSLayoutConstraint?
    
    lazy var alternateTabBar: UITabBar = {
        UITabBar()
    }()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        if self.alternateTabBarActive {
            self.tabBar.isHidden = true
            
            self.alternateTabBar.items = self.tabBar.items
            self.alternateTabBar.selectedItem = self.tabBar.selectedItem
            
            if UIDevice.current.userInterfaceIdiom == .pad {
                // Add Custom Tabbar
                let tabbar = self.alternateTabBar
                self.view.addSubview(tabbar)
                
                // Add layout constraints
                tabbar.translatesAutoresizingMaskIntoConstraints = false
                let bottom = tabbar.bottomAnchor.constraint(equalTo: self.view.bottomAnchor)
                let leading = tabbar.leadingAnchor.constraint(equalTo: self.view.leadingAnchor)
                let trailing = tabbar.trailingAnchor.constraint(equalTo: self.view.trailingAnchor)
                let height = NSLayoutConstraint(item: self.alternateTabBar, attribute: .height, relatedBy: .equal,
                                                toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 1)
                self.tabBarHeightConstraint = height
                self.view.addConstraints([bottom, leading, trailing, height])
            }
        }
    }

    override func viewWillLayoutSubviews() {
        super.viewWillLayoutSubviews()
        
        if self.alternateTabBarActive {
            self.alternateTabBar.items = self.tabBar.items
            self.alternateTabBar.selectedItem = self.tabBar.selectedItem
        }
    }
    
    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        
        if self.alternateTabBarActive {
            // Adjust height constraint
            let height = self.alternateTabBar.intrinsicContentSize.height
            self.tabBarHeightConstraint?.constant = height
            
            // Set insets for child view controllers
            let bottomInset = self.alternateTabBar.frame.size.height-self.view.safeAreaInsets.bottom
            self.viewControllers?.forEach { $0.additionalSafeAreaInsets = UIEdgeInsets(top: 0, left: 0, bottom: bottomInset, right: 0) }
        }
    }

}