StackoverFlow Example

StackoverFlowExample

https://stackoverflow.com/questions/45250787/ios-correctly-adopting-a-view-into-an-already-visible-parent

extension UIViewController {
    
    func adopChilViewController(_ childViewController: UIViewController) {
        addChildViewController(childViewController)
        view.addSubview(childViewController.view)
        childViewController.didMove(toParentViewController: self)
    }
}

class ViewController1 : UIViewController {
    
    let vc2 = ViewController2()
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        view.addSubview(addChildButton)
        view.addSubview(pushButton)
        
        addChildButton.frame = CGRect(x: 0.0, y: 64,
                              width: view.bounds.width, height: 100)
        
        pushButton.frame = CGRect(x: 0.0, y: 164,
                               width: view.bounds.width, height:100)
    }
    
    func addVC2() {
        adopChilViewController(vc2)
        
        vc2.view.backgroundColor = UIColor.yellow
        vc2.view.frame = CGRect(x: 0.0, y: 264,
                                width: view.bounds.width, height: 100)
    }
    
    func pushVC3() {
        navigationController?.pushViewController(ViewController3(), animated: true)
    }
    
    lazy var addChildButton : UIButton = {
        let button = self.newButtonWith(title: "Add Child (ViewController2)",
                                        selector : #selector(ViewController1.addVC2))
        return button
    }()
    
    lazy var pushButton : UIButton = {
        let button = self.newButtonWith(title: "Push View (ViewController3)",
                                        selector : #selector(ViewController1.pushVC3))
        return button
    }()
}

class ViewController2 : UIViewController {
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        print("ViewController2 viewWillAppear")
    }
    
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        print("ViewController2 viewDidAppear")
    }
    
    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillAppear(animated)
        print("ViewController2 viewWillDisappear")
    }
    
    override func viewDidDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        print("ViewController2 viewDidDisappear")
    }
}

class ViewController3 : UIViewController {
    
    override func viewWillAppear(_ animated: Bool) {
        view.addSubview(popViewControllerButton)
        popViewControllerButton.frame = CGRect(x: 0.0, y: 64, width: view.bounds.width, height: 100)
    }
    
    lazy var popViewControllerButton : UIButton = {
        let button = self.newButtonWith(title: "Pop Current ViewController3",
                                        selector : #selector(ViewController3.popVC3))
        return button
    }()
    
    func popVC3() {
       self.navigationController?.popViewController(animated: true)
    }
}

extension UIViewController {
    
    func newButtonWith(title : String, selector : Selector) -> UIButton {
       
        let button = UIButton(type: .custom)
        button.backgroundColor = UIColor.black
        button.setTitle(title, for: .normal)
        button.addTarget(self, action: selector, for: .touchUpInside)
        return button
    }
}