UIPageViewController load ChildViews multiple times - swift

Question

I've subclassed UIPageViewController, and it works fine. Except the fact that going back and forth load new instances of the pages, instead of (as i would expect) retrieving the instance it loaded previously.
Aren't the references supposed to be strong?
Following is my code.
Thank you for your help.
Pierrick
class CustomPageViewController: UIPageViewController, UIPageViewControllerDataSource {
var view1: FirstCustomViewController!
var view2: SecondCustomViewController!
var view3: ThirdCustomViewController!
var views = []
override func viewDidLoad() {
super.viewDidLoad()
self.dataSource = self;
self.view1 = FirstViewController()
self.view2 = SecondViewController()
self.view3 = ThirdViewController()
self.views = [self.view1, self.view2, self.view3]
self.setViewControllers([self.view1], direction: UIPageViewControllerNavigationDirection.Forward, animated: true, completion: nil)
}
// MARK: - PageViewControllerDataSource
func pageViewController(pageViewController: UIPageViewController, viewControllerBeforeViewController viewController: UIViewController) -> UIViewController? {
let index = self.views.indexOfObject(viewController)
if (index > 0) {
return self.views.objectAtIndex(index-1) as? UIViewController
}
return nil
}
func pageViewController(pageViewController: UIPageViewController, viewControllerAfterViewController viewController: UIViewController) -> UIViewController? {
let index = self.views.indexOfObject(viewController)
if (index < self.views.count-1) {
return self.views.objectAtIndex(index+1) as? UIViewController
}
return nil
}
}

Answer 1

Seems like the faulty function is in FirstViewController, SecondViewController, ThirdViewController. When i wrote my question, the view controller loaded the view following the method "viewWillAppear".
As soon as i moved the code to "viewDidLoad", the views stopped to load multiple times.