How do you implement switching between sections in an app that uses a tab bar with three tabs?

To implement switching between sections with a tab bar in iOS, UITabBarController is usually used. It manages multiple view controllers, each corresponding to a tab.

Example:

let tabBarController = UITabBarController()

let firstVC = FirstViewController()
firstVC.tabBarItem = UITabBarItem(title: "First", image: nil, tag: 0)

let secondVC = SecondViewController()
secondVC.tabBarItem = UITabBarItem(title: "Second", image: nil, tag: 1)

let thirdVC = ThirdViewController()
thirdVC.tabBarItem = UITabBarItem(title: "Third", image: nil, tag: 2)

// Set the view controllers of the tab bar

tabBarController.viewControllers = [firstVC, secondVC, thirdVC]

// To switch programmatically, you can change the `selectedIndex`
// tabBarController.selectedIndex = 1

The user switches between tabs by tapping on tab bar items, and programmatically, you can change the selectedIndex or selectedViewController property.