Swift 2：“布尔值”不可转换为 'BooleanLiteralConvertible'

Question

我在 XCode 6 中创建了一个应用程序。今天我下载了 XCode 7，它已将我的应用程序更新为 Swift 2。有很多错误，但现在只有一个我无法解决。我不知道为什么，但是 Xcode 不喜欢 animated 的任何 Bool 选项并显示此错误 -

'Bool' is not convertible to 'BooleanLiteralConvertible'

（如果你看一下函数本身，你会发现，animated 正好需要 Bool）

var startVC = self.viewControllerAtIndex(indexImage) as ContentViewController
var viewControllers = NSArray(object: startVC)

self.pageViewContorller.setViewControllers(viewControllers as [AnyObject], direction: UIPageViewControllerNavigationDirection.Forward, animated: true, completion: nil)
    'Bool' is not convertible to 'BooleanLiteralConvertible'

有人知道吗，我该如何解决？

谢谢。

Answer 1

Swift 很困惑，给你一个不正确的错误信息。问题是第一个参数是 [UIViewController]? 类型，所以下面应该有效：

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

或者更好的是，将 viewControllers 声明为 [UIViewController] 类型，然后在调用中不需要转换：

let viewControllers:[UIViewController] = [startVC]
self.pageViewContorller.setViewControllers(viewControllers, direction: UIPageViewControllerNavigationDirection.Forward, animated: true, completion: nil)

Answer 2

尽可能避免投射。 Swift 1 declaration for - setViewControllers:direction:animated:completion: 已更改为：

func setViewControllers(_ viewControllers: [AnyObject]!,
          direction direction: UIPageViewControllerNavigationDirection,
           animated animated: Bool,
         completion completion: ((Bool) -> Void)!)

到

func setViewControllers(viewControllers: [UIViewController]?,
          direction: UIPageViewControllerNavigationDirection,
           animated: Bool,
         completion: ((Bool) -> Void)?)

所以你的转换混淆了 Swift 2 因为 viewControllers 的类型 [AnyObject] 与 [UIViewController]? 不匹配。预计将来会审计更多 Objective-C 个 API。

首先将viewControllerAtIndex修改为return一个UIViewController:

func viewControllerAtIndex(index: Int) -> UIViewController {
    ...
}

然后让Swift推断出正确的类型：

let startVC = viewControllerAtIndex(indexImage)

let viewControllers = [startVC]

pageViewController.setViewControllers(viewControllers,
    direction: .Forward, animated: true, completion: nil)

这是以下的可读版本：

let startVC: UIViewController = viewControllerAtIndex(indexImage)

let viewControllers: [UIViewController] =
    Array<UIViewController>(arrayLiteral: startVC)

pageViewController.setViewControllers(viewControllers,
    direction: UIPageViewControllerNavigationDirection.Forward,
    animated: true, completion: nil)

Swift 2：“布尔值”不可转换为 'BooleanLiteralConvertible'

Swift 2: "Bool' is not convertible to 'BooleanLiteralConvertible'

ios

xcode

swift

uipageviewcontroller

swift2