Question

我试图创建通用的UIPageViewControlller，为此我想在协议扩展中使用默认实现，但我得到了这个堰错误

Objective-C方法'pageViewController：viewControllerBefore：'提供通过方法'pageViewController（_：viewControllerBefore :)'不匹配需求的选择器（ 'pageViewController：viewControllerBeforeViewController：'）

这就是我的代码的样子

protocol ViewModel {}

protocol PagerCard: class {
    var viewModel: ViewModel? { get set }
}


protocol Pager: UIPageViewControllerDataSource {

    associatedtype Card: UIViewController, PagerCard
    associatedtype CardModel: ViewModel
    var pagerController: UIPageViewController! { get set }
    var cards: Array<Card> { get set }
    var cardModels: Array<CardModel> { get set }

    func cardFactory() -> Card
    func viewControllerAtIndex(_ index: Int) -> Card?
}

extension Pager {
    func viewControllerAtIndex(_ index: Int) -> Card? {
        if (cardModels.count == 0) ||
            (index >= cardModels.count || index < 0) {
            return nil
        }

        // Get already configured controller
        if self.cards.count > index {
            return self.cards[index]
        }

        let cardVC = self.cardFactory()
        cardVC.viewModel = cardModels[index]
        cards.append(cardVC)
        return cardVC
    }

    func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
        let index = self.cards.index(of: viewController as! Card )!
        return self.viewControllerAtIndex(index - 1)
    }

    func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
        let index = self.cards.index(of: viewController as! Card)!
        return self.viewControllerAtIndex(index + 1)
    }
}

问题在于最后两种方法的Pager扩展，xcode抱怨函数声明但它们与UIPageViewControllerDataSource完全相同，如果我在UIViewController中使用完全相同的代码，一切正常。有任何想法吗？？谢谢

协议扩展中的UIPageViewControllerDataSource的默认实现不起作用

0 个答案: