iOS Present modal view controller on startup without flash

Question

I\'d like to present modally, at first startup, a tutorial wizard to the user.

Is there a way to present a modal UIViewController on application startup

Answer 1

This problem still exists in iOS 10. My fix was:

1. in viewWillAppear add the modal VC as a childVC to the rootVC
2. in the viewDidAppear:
   1. Remove the modalVC as a child of the rootVC
   2. Modally present the childVC without animation

Code:

extension UIViewController {

    func embed(childViewController: UIViewController) {
        childViewController.willMove(toParentViewController: self)

        view.addSubview(childViewController.view)
        childViewController.view.frame = view.bounds
        childViewController.view.autoresizingMask = [.flexibleHeight, .flexibleWidth]

        addChildViewController(childViewController)
    }


    func unembed(childViewController: UIViewController) {
        assert(childViewController.parent == self)

        childViewController.willMove(toParentViewController: nil)
        childViewController.view.removeFromSuperview()
        childViewController.removeFromParentViewController()
    }
}


class ViewController: UIViewController {

    let modalViewController = UIViewController()

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

        //BUG FIX: We have to embed the VC rather than modally presenting it because:
        // - Modal presentation within viewWillAppear(animated: false) is not allowed
        // - Modal presentation within viewDidAppear(animated: false) is not visually glitchy
        //The VC is presented modally in viewDidAppear:
        if self.shouldPresentModalVC {
            embed(childViewController: modalViewController)
        }
        //...
    }


    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        //BUG FIX: Move the embedded VC to be a modal VC as is expected. See viewWillAppear
        if modalViewController.parent == self {
            unembed(childViewController: modalViewController)
            present(modalViewController, animated: false, completion: nil)
        }

        //....
    }
}