How to prevent present modally an active controller?

Question

We have 2 controllers: MainVC and ProfileVC. From MainVC we go to ProfileVC with profileButton press (left item on navigation bar).

In Profile VC we hav

Answer 1

There may be another case for other developers:

Is the target ViewController presented after a connection triggered by a button? The user may be clicking twice, making two connections and opening the same ViewController twice, if you have a shared instance of the said ViewController.

Prevent it by doing something like this:

var didSuccess = false

func success(result: LoginModel.Result) {
    if didSuccess {
        return
    }
    didSuccess = true
    present(MainTabBarController.sharedInstance, animated: true, completion: nil)
}

Or disabling the button during connection.