How to Share Data Between Tab View Controllers

How to pass data between view controller and the tab-bar's view controllers using segue?

I got my answer

    @IBAction func submitButonTapped(_ sender: Any) {
            performSegue(withIdentifier: "homePage", sender: self)
    }
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        let barViewControllers = segue.destination as! UITabBarController
        let destinationViewController = barViewControllers.viewControllers![0] as! ViewControllerB
        destinationViewController.containsData = Data
    }

How to pass data between View Controllers in UITabBarController?

No, You can not pass the data between two ViewController directly, if they are connected to TabbArController.

If you want you can manage through NotificationCenter (So when a new change occur and you post the notification, it will automatically refresh the data)

NotificationCenter.default.addObserver(
            self,
            selector: #selector(self.getData),
            name: .refreshAttendanceForSelectedDate,
            object: nil)

@objc func getData() {
/// perform task in view controller
}

// post the changes when you get response ....

NotificationCenter.default.post(name: Constants.Notification.refreshAttendanceForSelectedDate, object: nil)

Or
You can pass the updated data by DataStorgae in a variable of that respective model type (LocalCache) by creating a singleton object. This variable will reside in memory till the app will reside in memory. After forcing kill the app or flush out the app from memory, this variable will automatically be removed.

Note: If needed, please don't forget to set value nil. (Eg. on logout action)

class DataStorage {
    
    /// Created the singleton objectbas
    static let instance = DataStorage()
    
   /// Created the properties
    var notificationbadgeCount: Int?
    var configData: ConfigurationModel?    
}

Use by set

DataStorage.instance.selectedStaffId = model.id

get the value

if let id = DataStorage.instance.selectedStaffId {
/// Perform respective task ....
}

Transfer data from tab bar controller to ViewController

What you want to do is, add a property called number, or whatever you like, to your ViewController class.

class ViewController: UIViewController {
  var number: Int!
}

Then in tabBarController's viewDidLoad, loop through the view controllers, check if they are of type ViewController, and then set their number property to the index of the tabBarController's view controllers:

class TabBarController: UITabBarController {

  override func viewDidLoad() {
    super.viewDidLoad()
    for (index,vc) in (viewControllers!.enumerated())! {
      if let viewController = vc as? ViewController {
        vc.number = index
      }
    }
  }

  override func tabBar(_ tabBar: UITabBar, didSelect item: UITabBarItem!) {
    if item == (self.tabBar.items as! [UITabBarItem])[0]{
      print(1)
    }
    else if item == (self.tabBar.items as! [UITabBarItem])[1]{
      print(2)
    }
  }

}

Unless, are you wanting to set the value whenever the tab is selected?

Best practice when sharing data/models between tabs of a TabBarController in Swift

let tabBar = tabBarController as! ExampleTabsController

But what if your ExampleViewController's tabBarController will be other UITabBarController or nil? Your architecture will stop working.
Your ExampleTabsController and FirstController are coupled very hard.
I can suggest you a little fix:

Add reference to your model inside FirstViewController:

var model: ExampleModel?

Inject it in your ExampleTabsController's loadViewControllers() function:

firstViewController.model = self.exampleModel

Now your ExampleTabsController and FirstViewController are not coupled.

pass data from tabbar controller to view controller in swift and xcode

Take a look at the documentation for the tab bar controller, in particular the viewControllers property.

That property is an array of UIViewControllers, in the order they appear in the tab bar, so you can pick the one you need (viewControllers[0] from your screen shot), cast it to your specific view controller subclass and then pass it your data.

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