Swift-運算符后的期望表達式（錯誤）

Question

我在以下代碼中有2個錯誤，原因相同。 我該如何解決？

錯誤顯示兩行上的“運算符之后的期望表達式”在最后兩個函數中return viewControllerAtIndex(index) 。

func viewControllerAtIndex(index: Int) -> WalkthroughContentViewController? {

    if index == NSNotFound || index < 0 || index >= pageHeadings.count {
        return nil
    }

    // Creating a new view controller and passing the data
    if let pageContentViewController = storyboard?.instantiateViewControllerWithIdentifier("WalkthroughContentViewController") as? WalkthroughContentViewController {

        pageContentViewController.imageFile = pageImages[index]
        pageContentViewController.heading = pageHeadings[index]
        pageContentViewController.content = pageContent[index]
        pageContentViewController.index = index

        return pageContentViewController
    }

    return nil
}


func pageViewController(pageViewController: UIPageViewController, viewControllerAfterViewController viewController: UIViewController) -> UIViewController? {

    var index = (viewController as! WalkthroughContentViewController).index
    index ++

    return viewControllerAtIndex(index)
}

func pageViewController(pageViewController: UIPageViewController, viewControllerBeforeViewController viewController: UIViewController) -> UIViewController? {

    var index = (viewController as! WalkthroughContentViewController).index
    index --

    return viewControllerAtIndex(index)
}

這是西蒙·伍的《雨燕書》。

Answer 1

問題是目標和后綴增量/減量運算符之間的空間。 應該是index++和index-- 。