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ViewController.swift

import UIKitclass ViewController: UIViewController{
           // Create a class variable for designation method to visit its attributes.    let labelOne = UILabel();        // Create a class variable for clourse to visit.    var mainContent: String = "";        @objc func mainListener(){
           let svc = SecondViewController();        // Create an optional closure to get the variable.        svc.closure = {
   (data: String) in            self.mainContent = data;            self.labelOne.text = self.mainContent;            print(self.mainContent);        }        self.present(svc, animated: true, completion: nil);    }        override func viewDidLoad() {
           super.viewDidLoad()        // Do any additional setup after loading the view.        //        let labelOne = UILabel(frame: CGRect(x: 30, y: 120, width: 240, height:30));        labelOne.frame = CGRect(x: 30, y: 120, width: 240, height:30);        labelOne.text = "Fuyang Normal Colleage";        labelOne.textColor = UIColor.purple;        labelOne.font = UIFont.boldSystemFont(ofSize: 20);        self.view.addSubview(labelOne);                let butttonOne = UIButton(type: UIButton.ButtonType.system);        butttonOne.frame = CGRect(x: 200, y:400, width: 100, height: 30);        butttonOne.setTitle("ButtonOne", for: UIControl.State())        self.view.addSubview(butttonOne);                butttonOne.addTarget(self, action: #selector(mainListener), for: UIControl.Event.touchUpInside);    }    }

SecondViewController.swift

import UIKitclass SecondViewController: UIViewController {
           // Create an optional clourse.    var closure: ((String) -> Void)?;        @objc func secondListener(){
           // Set the content into clourse.        self.closure!("Fuyang Normal University");        self.dismiss(animated: true, completion: nil);    }    override func viewDidLoad() {
           super.viewDidLoad()                self.view.backgroundColor = UIColor.orange;                let butttonOne = UIButton(type: UIButton.ButtonType.system);        butttonOne.frame = CGRect(x: 100, y:300, width: 120, height: 30);        butttonOne.setTitle("Second", for: UIControl.State())        self.view.addSubview(butttonOne);                butttonOne.addTarget(self, action: #selector(secondListener), for: UIControl.Event.touchUpInside);        // Do any additional setup after loading the view.    }}

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