Why viewDidLoad function is not called? - ios

Question

I want to change UIBarButton's color in the navigationBar. To achieve this, in viewDidLoad: I put this line:
navigationController?.navigationBar.tintColor = .white
Everything works fine until I started to notice something strange. That UIBarButton is used to dismiss the UIViewController. When it is pressed, I just dismiss the viewController. But, if I present it (viewController) again, the color of the UIBarButton is not white, it gets tintColor of the application.
After doing some debugging, I noticed that viewDidLoad: is not called again after the viewController is just dismissed and presented again. The reason why my UIBarButton has a different color is because I change its color in viewDidLoad:. When viewDidLoad: is not called, of course, color is not changed.
It was an interesting discovery for me the fact that iOS doesn't call viewDidLoad: for UIViewController that was presented already. Possibly, it is due to the optimisation, because it is not efficient to draw the whole UI every time.
My solution to this problem can be to change color, not in viewDidLoad:, but in viewDidAppear:. But, is it right approach to solve a problem? And why viewDidLoad: is not called in the above situation?

Answer 1

It looks like you create and store you view controller, but present it wrapped in UINavigationController:
let controller = YourModalViewController()
...
func presentMyModal() {
present(UINavigationController(rootViewController: controller))
}
In this case your viewDidLoad method will be called just once and you'll have visual bug. If you want to leave styling code of your modal inside it's file you can create instance func which will return this controller wrapped and styled.
extension YourModalViewController {
func wrappedInNC() -> UINavigationController {
let nc = UINavigationController(rootViewController: controller)
// Styling code.
return nc
}
}