ios - 类型 'PageViewController' 不符合协议(protocol) 'UIPageViewControllerDataSource'

Question

我一直在尝试在 Storyboard中使用 UIPageViewController 来创建一组滑动图像，但我一直收到此错误:

Type 'PageViewController' does not conform to protocol 'UIPageViewControllerDataSource'

我不明白为什么。

class PageViewController: UIPageViewController, UIPageViewControllerDelegate, UIPageViewControllerDataSource {

    //for scroll view
    lazy var subViewControllers:[UIViewController] = {
        return[
            UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "Slide_1") as! ViewController_0,
            UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "Slide_2") as! ViewController_1,
            UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "Slide_3") as! ViewController_2
        ]
    }()

    //after viewcontroller
    func pageViewController(_pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
        let currentIndex:Int = subViewControllers.index(of: viewController) ?? 0
        if (currentIndex >= subViewControllers.count - 1) {
            return nil
        }
        return subViewControllers[currentIndex + 1]
    }

    //before viewcontroller
    func pageViewController(_pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
        let currentIndex:Int = subViewControllers.index(of: viewController) ?? 0
        if (currentIndex <= 0) {
            return nil
        }
        return subViewControllers[currentIndex - 1]
    }
    override func viewDidLoad() {
        super.viewDidLoad()
    //setting the initial view for the slider
        setViewControllers([subViewControllers[0]],direction: .forward, animated: true, completion: nil)
    }
    //making style a normal slide
    required init?(coder: NSCoder) {
        super.init(transitionStyle: .scroll, navigationOrientation: .horizontal, options: nil)
    }
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    // MARK: - Navigation
    func presentationCount(for pageViewController: UIPageViewController) -> Int {
        return subViewControllers.count
    }
}

Answer 1

在作为协议(protocol)一部分的两个方法中，_ 和 pageViewController 参数之间应该有一个空格(前/后页面)。

下划线表示该方法在调用时不需要该参数的标签。

例如:

func setBlob(_ blob: Blob) -> Bool {
}

调用时看起来像这样:

let myBlob = Blob()
setBlob(myBlob)

如果那里没有 _，它会期望 setBlob(blob: blob)。为了代码整洁起见，能够更改或忽略参数名称很方便。但是由于参数标签和实际参数名称之间没有空格，它认为参数名称是 _pageViewController。

在错误显示的同一行上应该有一个红色图标，您可以单击该图标自动填充缺失的方法，这样您就可以轻松查看缺失/不正确的内容。您的类必须实现协议(protocol)的所有必需方法并遵循相同的方法签名，否则您将收到此错误。