Dismiss a ViewController and present another ViewControlloer - IOS - Swift 3

Question

I would like to dismiss a ViewController and present another ViewController. Here is my code:

MainVC:

@IBAction func loadFirstVCClicked(_ sender: UIButton)
{
    self.present(FirstViewController.loadVC()
}

FirstViewController:

static func load() -> FirstViewController
{
    let vc = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "FirstViewController") as! FirstViewController
    return vc
}
@IBAction func exitClicked(_ sender: UIButton)
{
    self.dismiss(animated: true, completion: {
        self.present(SecondViewController.loadVC()
    })
}

SecondViewController:

static func loadVC() -> SecondViewController
{
    let vc = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "SecondViewController") as! SecondViewController
    return vc
}

@IBAction func exitClicked(_ sender: UIButton)
{
    self.dismiss(animated: true, completion: {
        //present MainVC - second VC should work as an interstitial ad
    })
}

And I get this error: "SecondViewController on FirstViewController whose view is not in the window hierarchy!"

And it doesn't get displayed. So basically I want the SecondViewController to be a sort of interstitial ad between the dissmisal of SecondViewController and the MainVC didLoad

A basic scheme:

FirstViewController->SecondViewController->MainVC

Any suggestions from you would really be appreciated. Thank you!

Answer 1

You should not use static functions to create viewcontrollers. The proper way of displaying interstitial first open mainviewcontroller and onViewDidAppear show your ad viewcontroller

@IBAction func loadFirstVCClicked(_ sender: UIButton)
{
    let firstViewController = self.storyboard?.instantiateViewController(withIdentifier: "FirstViewController") as! FirstViewController
    self.present(firstViewController)
}

@IBAction func loadMainVCClicked(_ sender: UIButton)
{
    let mainViewController = self.storyboard?.instantiateViewController(withIdentifier: "MainViewController") as! MainViewController
    self.present(firstViewController)
}

class MainViewController: UIViewController {

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)

        // there you can present your interstitial viewcontroller
    }

}

class InterstitialViewController: UIViewController {

    // when user press close or after a time limit dismiss 

}

A protocol (delegate) sample

// give the name you want
protocol LiveProtocol: class {

    func onFirstViewControllerDismissed()

}

And your live viewcontroller before firstviewcontroller

class LiveViewController: UIViewController, LiveProtocol {

    ...

    internal func onFirstViewControllerDismissed() {

        // present your interstitial 

    }

}