Selected Index on Tab Bar not working on Swift - ios

Question

I want to change the default selected view controller of a UITabBar / UITabBarController via selectedIndex.
I tried other solutions I saw in other threads, like changing it in the AppDelegate or in ViewDidAppear like this:
class MainTabBarController: UITabBarController {
override func viewDidLoad() {
super.viewDidLoad()
setupTabBar()
}
override func viewDidAppear(_ animated: Bool) {
// this is the attempt to set the selected index that doesn't work
self.tabBarController?.selectedIndex = 2
}
func setupTabBar(){
let vc1 = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "mainvc")
let vc2 = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "secondvc")
let vc3 = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "thirdvc")
let FirstController = UINavigationController(rootViewController: vc1)
let SecondController = UINavigationController(rootViewController: vc2)
let ThirdController = UINavigationController(rootViewController: vc3)
viewControllers = [FirstController, SecondController, ThirdController]
}
}
Nothing worked so far, and it always shows the selected index = 0.
I set the tab bar view controller as the initial view controller in the Main storyboard. Should I be doing this in the AppDelegate instead?

Answer 1

You are saying that
class MainTabBarController: UITabBarController {
so self refers to a UITabBarController, but you are setting the selected index of tabBarController of self:
self.tabBarController?.selectedIndex = 2
There are no tab bar controllers embedded in self. self itself is a tab bar controller! You can just set self.selectedIndex:
self.selectedIndex = 2
Also, you should do that in viewDidLoad instead of viewDidAppear, because viewDidAppear can happen many times (every time some modal controller is dismissed for example). viewDidLoad will only be called once.