UIPageViewController错误的访问错误

Question

I know the error means I have a NULL pointer, but I am unsure as to WHY that is, and I assume it must be something I did wrong in my code. My index starts at 1 because I want it to start in the middle view controller which is the home page. I am trying to make a page view controller to swipe between view controllers similar to snapchat. I have the following code:

import UIKit

class PageViewController: UIPageViewController, UIPageViewControllerDelegate, UIPageViewControllerDataSource {

  var viewControllersArray = [UIViewController]()
  var pageIndex: Int?
  let selectedIndex = 1

  override func viewDidLoad() {
    super.viewDidLoad()

    self.view.backgroundColor = UIColor.clearColor()

    let vc1 = storyboard?.instantiateViewControllerWithIdentifier("ProfileView") as! ProfileViewController
    let vc2 = storyboard?.instantiateViewControllerWithIdentifier("HomeView") as! HomeViewController
    let vc3 = storyboard?.instantiateViewControllerWithIdentifier("MatchesView") as! MatchViewController

    viewControllersArray.append(vc1)
    viewControllersArray.append(vc2)
    viewControllersArray.append(vc3)

    self.dataSource = self

    let pageContentViewController = self.viewControllerAtIndex(selectedIndex)
    self.setViewControllers([pageContentViewController!], direction: UIPageViewControllerNavigationDirection.Forward, animated: true, completion: nil)  //Error here

  }

the error occurs at this line:

self.setViewControllers([pageContentViewController!], direction: UIPageViewControllerNavigationDirection.Forward, animated: true, completion: nil)  //Error here

The error is as follows: "Thread 1: EXC_BAD_ACCESS(code=2, address=0x7fff58d57ff8)

Here is my viewControllerAtIndex function:

func viewControllerAtIndex(index : Int) -> UIViewController? {
   if((self.viewControllersArray.count == 0) || (index >= self.viewControllersArray.count)) {
     return nil
   }

   let pageContentViewController = self.storyboard?.instantiateViewControllerWithIdentifier("PageViewController") as! PageViewController
   pageContentViewController.pageIndex = index


   return pageContentViewController
}

Here is my storyboard with the view controllers to swipe between:

Any and all help is greatly appreciated!

Answer 1

It looks like

func viewControllerAtIndex(index : Int) -> UIViewController? {
   if((self.viewControllersArray.count == 0) || (index >= self.viewControllersArray.count)) {
     return nil
   }

   let pageContentViewController = self.storyboard?.instantiateViewControllerWithIdentifier("PageViewController") as! PageViewController
   pageContentViewController.pageIndex = index


   return pageContentViewController
}

Needs to be:

func viewControllerAtIndex(index : Int) -> UIViewController? {
   if((self.viewControllersArray.count == 0) || (index >= self.viewControllersArray.count)) {
     return nil
   }

   return viewControllersArray[index]
}

Additionally

let selectedIndex = 1

should be

let selectedIndex = 0

since 1 will refer to the second page.