I was trying to make a tutorial screen in my iOS app where the user swipes past a few pictures to learn a bit about the said application. Everything looks fine, except when I build my project, I get the following error on the very first line of code:
Class ViewController has no initializers
What did I do wrong?
My ViewController.swift code is below
import UIKit
//line below is where I get the error
class ViewController: UIViewController, UIPageViewControllerDataSource {
//end
var pageViewController: UIPageViewController
var pageTitles: NSArray!
var pageImages: NSArray!
override func viewDidLoad() {
super.viewDidLoad()
self.pageTitles = NSArray(objects: "", "", "")
self.pageImages = NSArray(objects: "page1", "page2", "page3")
self.pageViewController = self.storyboard?.instantiateViewControllerWithIdentifier("PageViewController") as!
UIPageViewController
self.pageViewController.dataSource = self
var startVC = self.viewControllerAtIndex(0) as ContentViewController
var viewControllers = NSArray(object: startVC)
self.pageViewController.setViewControllers(viewControllers as [AnyObject], direction: .Forward, animated: true, completion: nil)
self.addChildViewController(self.pageViewController)
self.view.addSubview(self.pageViewController.view)
self.pageViewController.didMoveToParentViewController(self)
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
@IBAction func restartAction(sender: AnyObject) {
}
func viewControllerAtIndex(index: Int) -> ContentViewController
{
if ((self.pageTitles.count == 0) || (index >= self.pageTitles.count))
{
return ContentViewController()
}
var vc: ContentViewController = self.storyboard?.instantiateViewControllerWithIdentifier("ContentViewController") as! ContentViewController
vc.imageFile = self.pageImages[index] as! String
vc.titleText = self.pageTitles[index] as! String
vc.pageIndex = index
return vc
}
// Mark: - Page View Controller Data Source
func pageViewController(pageViewController: UIPageViewController, viewControllerBeforeViewController viewController: UIViewController) -> UIViewController? {
var vc = viewController as! ContentViewController
var index = vc.pageIndex as Int
if (index == 0 || index == NSNotFound)
{
return nil
}
index--
return self.viewControllerAtIndex(index)
}
func pageViewController(pageViewController: UIPageViewController, viewControllerAfterViewController viewController: UIViewController) -> UIViewController? {
var vc = viewController as! ContentViewController
var index = vc.pageIndex as Int
if (index == NSNotFound)
{
return nil
}
index++
if (index == self.pageTitles.count)
{
return nil
}
return self.viewControllerAtIndex(index)
}
func presentationCountForPageViewController(pageViewController: UIPageViewController) -> Int {
return self.pageTitles.count
}
func presentationIndexForPageViewController(pageViewController: UIPageViewController) -> Int {
return 0
}
}
It's because of this line:
var pageViewController: UIPageViewController
You're saying that pageViewController
cannot be null, but you don't have an initializer that sets it to a value. Looking at your code, I suspect you want to change it to this:
var pageViewController: UIPageViewController!
I went into more detail on this problem here.
In a Swift class each non-optional declared variable must be initialized in one of the given init methods.
In your case, it's this variable
var pageViewController: UIPageViewController
declare it as implicit unwrapped optional as the other two variables, because the variable is guaranteed to be set before it's used.
var pageViewController: UIPageViewController!
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