Cannot assign to property: 'self' is immutable

Question

I am creating a page view application. I have written code for the ViewController:

import UIKit

class ViewController: UIViewController {

var pageViewController : UIPageViewController!
var pageTitles : NSArray!
var pageImages : NSArray!

@IBAction func restartAction(sender: AnyObject) {}

override func viewDidLoad() {
    super.viewDidLoad()

    self.pageTitles = NSArray(objects: "This Is Page One!", "This Is Page Two!")
    self.pageImages = NSArray(objects: "page1", "page2")

    self.pageViewController = self.storyboard?.instantiateViewControllerWithIdentifier("PageViewController") as! UIPageViewController

    self.pageViewController.dataSource = self // <–– Error

    let startVC = self.viewControllerAtIndex(0) as ContentViewController
    let viewControllers = NSArray(object: startVC)

    self.pageViewController.setViewControllers(viewControllers as? [UIViewController], direction: .Forward, animated: true, completion: nil)

    self.pageViewController.view.frame = CGRectMake(0, 30, self.view.frame.width, self.view.frame.height - 60)

    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.
}

func viewControllerAtIndex(index: Int) -> ContentViewController {
    if ((self.pageTitles.count == 0) || (index >= self.pageTitles.count)) {
        return ContentViewController()
    }

    let 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
}



func pageViewController(pageViewController: UIPageViewController, viewcontrollerBeforeViewController viewController: UIViewController) ->UIViewController? {

    let 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? {

    let 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)

}

}

But I am getting an error on this line self.pageViewController.dataSource = self. The error is:

Cannot assign to property: 'self' is immutable

I am unsure of why self is immutable and how to fix it. If someone could please help, thanks in advance.

Answer 1

In swift you'll need to call self.pageViewController.setDelegate(self)

Delegates have been declared as methods, not properties in some cases