编译器错误:具有 Objective-C 选择器的方法与具有相同 Objective-C 选择器的先前声明冲突 [英] Compiler error: Method with Objective-C selector conflicts with previous declaration with the same Objective-C selector

问题描述

我开始学习 Swift，并且一直在关注 YouTube 上非常棒的斯坦福大学视频讲座.如果您有兴趣或有帮助，这里有一个链接(尽管理解我的问题不是必需的):

I am starting to learn Swift, and have been following the very good Stanford University video lectures on YouTube. Here is a link if you are interested or it helps (although it isn't required to understand my problem):

开发 iOS 8 应用使用 Swift - 2. 更多 Xcode 和 Swift、MVC

在听完讲座后，我发现(据我所知)我的代码与视频中的代码相同，但在我的系统上我遇到了编译器错误.经过大量的反复试验，我设法将我的代码减少到两个示例，其中一个生成错误，另一个生成错误，但我不知道实际导致错误的原因或如何解决它.

While following the lectures I got to a point where (as far as I could tell) my code was identical to the code in the video but on my system I got a compiler error. After a lot of trial and error I have managed to reduce my code to two examples, one of which generates an error, the other or which doesn't, but I have no idea what is actually causing the error or how to resolve it.

产生错误的代码是:

import UIKit

class BugViewController: UIViewController
{
    func perform(operation: (Double) -> Double) {
    }

    func perform(operation: (Double, Double) -> Double) {
    }
}

这会产生以下编译器错误:

This creates the following compiler error:

使用 Objective-C 选择器 'perform:' 的方法 'perform' 与具有相同 Objective-C 选择器的先前声明冲突

Method 'perform' with Objective-C selector 'perform: ' conflicts with previous declaration with the same Objective-C selector

通过简单地删除 UIViewController 的子类，代码编译:

By simply removing the sub-classing of UIViewController the code compiles:

import UIKit

class BugViewController
{
    func perform(operation: (Double) -> Double) {
    }

    func perform(operation: (Double, Double) -> Double) {
    }
}

其他一些可能相关或不相关的信息:

Some other information which may or may not be relevant:

• 我最近升级到了优胜美地.
• 当我安装 Xcode 时，我最终得到了 Beta 版本(版本 6.3 (6D543q))，因为(如果我没记错的话)这是我需要在我的 OS X 版本上运行的版本.

我有点希望这是编译器中的一个错误，否则这对我来说没有任何意义.非常感谢您的帮助！

I am half hoping this is a bug in the compiler because otherwise this doesn't make any sense to me. Any help very gratefully received!

推荐答案

Objective-C 不支持方法重载，您必须使用不同的方法名称.当您继承 UIViewController 时，您继承了 NSObject 并使该类可与 Obj-C 互操作.另一方面，Swift 确实支持重载，这就是为什么当您删除继承时它可以工作的原因.

Objective-C does not support method overloading, you have to use a different method name. When you inherited UIViewController you inherited NSObject and made the class interopable to Obj-C. Swift on the other hand does support overloading, that's why it works when you remove the inheritance.

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