Transparent background for modally presented viewcontroller

Fixed it.

The problem was that presentViewController does not keep the view that I was covering.

viewController.modalPresentationStyle = .overCurrentContext

did the trick.

Part of the solution is hidden in the question. You need three lines to make the background transparent, viz. isOpaque = false backgroundColor = .clear & set the modalPresentationStyle

Here's the full solution. In the calling View Controller, call this function:

func presentModal() {
    let modalController = ModalViewController()
    modalViewController.modalPresentationStyle = .overCurrentContext
    present(modalViewController, animated: true, completion: nil)
}

And in ModalViewController's viewDidLoad():

override func viewDidLoad() {
    super.viewDidLoad()

    view.isOpaque = false
    view.backgroundColor = .clear // try other colors, say: .white or black with Alpha etc.
}

same as the selected answer but visually through IB:

I have two view controller 1st login & 2nd forgot password. Initially, the login screen has been visible on the tap of forgot password button, forgot password screen will be present over the login screen with a transparent background.

In the Login screen, I have used following code for forgotButtonAction to present forgotPasswordViewController

   let vc = UIStoryboard.init(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "forgotPasswordViewController") as! forgotPasswordViewController
    vc.modalPresentationStyle = .overCurrentContext
    present(vc, animated: true, completion: nil)

And also in the forgotPasswordViewController, Under the ViewDidLoad method, I have to change the view background color and opaque state through the following code

   override func viewDidLoad() {
    super.viewDidLoad()
    view.isOpaque = false
    view.backgroundColor = .clear
   }