我试图弄清楚如何在
Xcode 7(iOS9)上的
Swift中解决这个问题,我也遇到了这个错误：
Cannot subscript a value of type ‘[UIViewController]?’ with an index of type ‘Int’
任何建议表示赞赏.谢谢.
我的代码：
func indexPositionForCurrentPage(pageViewController: UIPageViewController) -> Int {
let currentViewController = pageViewController.viewControllers[0] as UIViewController
for (index,page) in pages.enumerate() {
if (currentViewController == page) {
return index
}
}
return -1
}
解决方法
尝试：
let currentViewController = pageViewController.viewControllers![0]
但是,写一下会更安全：
if let currentViewController = pageViewController.viewControllers?[0] {
// ... and then do everything else in the if-block
end
另一种选择：
guard let currentViewController = pageViewController.viewControllers?[0] else {
return
}
// ... and then just proceed to use currentViewController here
这样做的好处是它安全,但不需要将函数的其余部分放在if块中.