Dismiss previous ViewController upon selecting UITabBarItem for second time - ios

Question

I work on an iOS application that implements a UITabBarController with 5 icons connected. The whole project is made via Storyboard. As I want to give the option for 4 themes to the user, which thing I do in a static tableView, I came across an issue.
When the user changes theme, the previously instantiated via the tabBar view controllers do not update to the theme change because they exist before the theme update. Can I somehow dismiss them and create new instances of the same view controller classes upon the didSelect method of the UITabBar delegate?
Am I approaching the issue correctly? Any help would be much appreciated!
Thanks you in advance for your help.
class MainTabController: UITabBarController
{
override func viewDidLoad()
{
super.viewDidLoad()
}
override func tabBar(_ tabBar: UITabBar, didSelect item: UITabBarItem)
{
let theme = UserDefaults.standard.string(forKey: "selectedColor")
print(theme!)
for vc in self.viewControllers!
{
if (theme == "default")
{
vc.view.backgroundColor = UIColor(red: 0xF9 , green: 0xF7 , blue: 0xF7)
}else if (theme == "theme1")
{
vc.view.backgroundColor = UIColor(red: 0x1F , green: 0xFF, blue: 0xFF)
}else if (theme == "theme2")
{
vc.view.backgroundColor = UIColor(red: 0xE3 , green: 0xFD, blue: 0xFD)
}else if (theme == "theme3")
{
vc.view.backgroundColor = UIColor(red: 0x3E, green: 0xC1, blue: 0xD3)
}
}
}
}
example of implementing in each view controller:
override func viewDidLoad()
{
let theme = UserDefaults.standard.string(forKey: "selectedColor")
print(theme!)
if (theme == "default")
{
outerView.backgroundColor = UIColor(red: 0xF9 , green: 0xF7 , blue: 0xF7)
}else if (theme == "theme1")
{
outerView.backgroundColor = UIColor(red: 0x1F , green: 0xFF, blue: 0xFF)
}else if (theme == "theme2")
{
outerView.backgroundColor = UIColor(red: 0xE3 , green: 0xFD, blue: 0xFD)
}else if (theme == "theme3")
{
outerView.backgroundColor = UIColor(red: 0x3E, green: 0xC1, blue: 0xD3)
}
}

Answer 1

Inside didSelect you can access the tab VCs and change them as you like ( inside any VC in the tab )
for vc in self.tabBarController!.viewControllers! {
vc.view.backgroundColor = UIColor.red
// if you want to set a property
if let other = vc as? OtherViewController {
// change here
}
}
//
if you want this code inside the tabBar custom class
for vc in self.viewControllers! {
vc.view.backgroundColor = UIColor.red
// if you want to set a property
if let other = vc as? OtherViewController {
// change here
}
}
//
after your edit , you need to either create a protocol containing the outerView and conform to this protocol in every VC or cast to the VC and change it's property

Answer 2

Create custom UITabBarController class and in it's viewDidLoad add :
for vc in self.viewControllers! {
vc.view.backgroundColor = .....
}
Now link this custom class to the Storyboard's UITabBarController.
Update :
You are getting the value from UserDefaults incorrectly.
UserDefaults.standard.string(forKey: "selectedColor")
It should be :
UserDefaults.standard.object(forKey: "selectedColor")

Answer 3

The solution to my problem was really simple but only after many hours of searching!
I had to put all my code that is editing the view in viewDidAppear instead of viewDidLoad because viewDidLoad is running only on the first time in contrast with
viewDidAppear which is called every time the user presses this particular tab.
Thank you all for your fast answers!