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

Answer 2

我认为编译器在这里不是很有帮助 - 尝试将控制器声明为以下数据源协议并查看是否修复了这个奇怪的错误

class ViewController: UIViewController, UIPageViewControllerDataSource {  etc