How do I pass data from a UIViewController to UITabBarController?

If the ViewController is a child of the UITabBarController that you want to access, you can simply use tabBarController property of the UIViewController, e.g., use this to change selected controller to the first one:

@IBAction func submitbutton(_ sender: UIButton) { pressed = true self.tabBarController?.selectedIndex = 0 } 

So let's say that you have a custom UITabBarController subclass, e.g.:

class CustomTabBarController: UITabBarController { func acceptData(points: Int) { print(">>> Accepted: \(points)") // or do anything you need to do with it } } 

Then you can pass it data as follows:

@IBAction func submitbutton(_ sender: UIButton) { pressed = true if let customTabController = self.tabBarController as? CustomTabBarController { customTabController.acceptData(points: self.points) } } 

UPDATE

Since it seems that the current VC is presented by one of the tabBarController child controllers, you will have to access it through the self.presentingViewController:

@IBAction func submitbutton(_ sender: UIButton) { pressed = true if let customTabController = self.presentingViewController?.tabBarController as? CustomTabBarController { customTabController.acceptData(points: self.points) } } 

UPDATE 2

Your screenshot are of a very poor quality, your explanation of the problem would require a clarification too, since it is really hard to understand what you try to do. So after the whole discussion in comments I guess this is it:

@IBAction func submitbutton(_ sender: UIButton) { pressed = true if let tabController = self.presentingViewController?.tabBarController, let viewController3 = tabController.viewControllers?.filter({ $0 is ViewController3 }).first { viewController3.acceptData(points: self.points) } } 

You can pass data as normally

 let vc:HomeVC = ApiUtillity.sharedInstance.getCurrentLanguageStoryboard().instantiateViewController(withIdentifier: "HomeVC") as! HomeVC vc.tempCategoryArray = CategoryArray self.navigationController?.pushViewController(vc, animated: true) 

In your TabBarController class, take a variable say variableToBeSet

class TabBarController: UITabBarController { var variableToBeSet: Int = 0 // This is just an example. You can change it as per requirement. // Rest of class implementation } 

Now in your ViewController :

@IBAction func submitbutton(_ sender: UIButton) { pressed = true let tabControllerInstance = self.tabBarController as! TabBarController tabControllerInstance.variableToBeSet = localVariable // The value which you want to assign }