Empty a UIPageViewController (remove ViewControllers inside) - ios

Question

How can I remove all the viewControllers inside a UIPageViewController in Swift?
Those calls:
pageViewController.setViewControllers(nil,....)
pageViewController.setViewControllers([UIViewController(),....)
both make my app crash with the following message:The number of view controllers provided (0) doesn't match the number required (1) for the requested transition

Answer 1

A UIPageViewController does not "hold view controllers" in the sense you are thinking of. All it does is display a view controller returned by its dataSource ... and its dataSource is your code.
If you simply do this:
[pageViewController setViewControllers:#[UIViewController.new] direction:UIPageViewControllerNavigationDirectionForward animated:NO completion:nil];
That will replace the current "page" with an empty UIViewController - but it won't do anything else. You'll still be able to scroll, and depending on your next/previous logic, that may result in other errors.
What you'll want to do is "clear" the current page with that line, but then also prevent scrolling / swiping. This is often done by setting the UIPageViewController's dataSource to nil.

Answer 2

What Don explained, for 2020:
As #DonMag has explained. Really all you can do is
Simply replace the current VC you are seeing, with, a blank one.
Set the datasource of the page view controller to null
Important caveats ..
• What does it really mean to have a "blank" VC in your app? It could be, you make as special view controller (which is just "gray clouds" or "an explanation that there is no data" or something) which you use.
• But you can in fact safely just use UIViewController() and it will be blank, nothingness.
• With point 2, don't forget to set it back!
In practice... something like...
var vcs: [UIViewController] = []
func reloadPages() {
print("reload pages in your page view controller")
let k = yourData.count
if k == 0 {
dataSource = nil
setViewControllers([UIViewController()], direction: .forward, animated: false)
return
}
dataSource = self
vcs = []
for i in 0..<k {
let vc = _sb("SomePageOfYours") as! SomePageOfYours
vcs.append(vc)
}
setViewControllers([vcs[0]], direction: .forward, animated: false)
}
In the last line of code, don't forget it's an array of only the first item, not the whole array.
Aside - the call '_sb' is just something that loads your view controller from it's storyboard. Example,
func _sb(_ s: String) -> UIViewController {
// assume the storyboard id is set as ClassNameID
return UIStoryboard(name: s, bundle: nil)
.instantiateViewController(withIdentifier: s + "ID")
}