扩展中的声明无法覆盖Swift 4中的错误 [英] Declarations in extensions cannot override yet error in Swift 4

问题描述

我有一个扩展名：

public extension UIWindow {
    override public func topMostController()->UIViewController? { ... }
}

但我的 topMostController 我收到下一个错误：

but for my topMostController I get the next error:

Declarations in extensions cannot override yet error

它适用于Swift 3.1，但对于Swift 4，我收到此错误。怎么修好？他们在Swift 4中有什么变化？

It works well for Swift 3.1, but for Swift 4 I get this error. How can it be fixed? What did they change in Swift 4?

推荐答案

如果你做基础实现它会工作 @objc 。有关内部结构的详细说明，请参见 Hamish的答案。

It will work if you make the base implementation @objc. See Hamish's answer for a detailed explanation about the internals.

在扩展中声明的重写方法有点难以正确执行。 Objective-C支持它，但它并不是绝对安全的。斯威夫特的目标是做得更好。该提案尚未完成。

Overriding methods declared in extensions is a bit tricky to do correctly. Objective-C supports it, but it's not absolutely safe. Swift aims to do it better. The proposal is not completed yet.

提案的当前版本这里。

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