UserDefaults from Swift Other Screen

import UIKit
import Foundation

class PostVC:UIViewController {

    @IBOutlet weak var textField: UITextField!

    vardata: String = [ ]

    let userDefaults=UserDefaults.standard

    override func viewDidLoad(){
        super.viewDidLoad()

        // Do any additional setup after loading the view.
    }

    @ IBAction funcellAdd(_sender:Any){
        guard let list = tabBarController ?.viewControllers ?[0] as ? ListVCelse{
            print("Cannot get listVC from tab bar controller")
            return
        }

        let postText=textField.text???"
        list.data.insert(postText, at:0)

        userDefaults.set(data, forKey: "DataStore")

        userDefaults.synchronize()

        list.tableView?.insertRows(at: IndexPath(row:0, section:0), with:.automatic)
    }

}

import UIKit

classListVC:UIViewController, UITableViewDataSource, UITableViewDelegate{

    @IBOutlet weak variableView:UITableView!

    vardata: String = [ ]

    let userDefaults=UserDefaults.standard

    override func viewDidLoad(){
        super.viewDidLoad()
        // Do any additional setup after loading the view.

        // <TableView Initial Configuration>
        tableView.dataSource=self
        tableView.delegate=self

        data=readData()
    }

    functableView(_tableView:UITableView, numberOfRowsInSection section:Int) - > Int{
        return data.count
    }

    functableView(_tableView:UITableView, cellForRowAtindexPath:IndexPath) - >UITableViewCell{
        let postcell=tableView.dequeueReusableCell(withIdentifier: "postcell")!
        postcell.textLabel?.text=data [indexPath.row]
        return postcell
    }

    funcreadData()->[String]{
        let dataArray=userDefaults.array(forKey: "DataStore") as?[String]??[]
        return dataArray
    }

}