UIDynamicAnimator项目(in :)在iOS 11中崩溃

问题描述

在iOS 11(Xcode 9 beta 5)中，我正在调用UIDynamicAnimator的items(in:)方法并立即崩溃:

In iOS 11 (Xcode 9 beta 5), I'm calling UIDynamicAnimator's items(in:) method and immediately crashing:

这是怎么回事?

推荐答案

您发现了一个错误. (向Apple提交，雷达33979954.)希望它会尽快修复，但在此之前，这里是修复方法:

You've found a bug. (Filed with Apple, radar 33979954.) Hopefully it will be fixed soon, but until then, here's the fix:

extension UIDynamicAnimator {
    func views(in rect: CGRect) -> [UIView] {
        let nsitems = self.items(in: rect) as NSArray
        return nsitems.flatMap{$0 as? UIView}
    }
}

现在调用view(in:)而不是items(in:)，一切都会好起来.

Now call view(in:) instead of items(in:), and all will be well.

问题是将虚假对象放入从items(in:)返回的数组中.由于存在这些虚假对象，因此数组无法跨越从Objective-C到Swift的桥梁；在Swift中将返回的数组键入为[UIDynamicItem]，但是该数组包含的内容不是UIDynamicItem对象.

The problem is that spurious objects are being put into the array returned from items(in:). Because of these spurious objects, the array cannot cross the bridge from Objective-C to Swift; the returned array is typed in Swift as [UIDynamicItem], but the array contains things that are not UIDynamicItem objects.

此扩展程序通过不越桥来解决此问题.我们留在NSArray Objective-C世界中，过滤掉虚假对象，然后然后过桥.

The extension works around this by not crossing the bridge. We stay in the NSArray Objective-C world, filter out the spurious objects, and then cross the bridge.

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