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。如果您有兴趣或它有帮助(尽管不需要理解我的问题)，这里有一个链接:

Developing iOS 8 Apps with Swift - 2. More Xcode and 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完全相同，但在我的系统上我遇到了编译器错误。经过大量的试验和错误后，我设法将我的代码减少到两个示例，其中一个生成错误，另一个生成错误或不生成错误，但我不知道究竟是什么导致了错误或如何解决它。

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:

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:

import UIKit

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

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

一些其他可能相关或不相关的信息:

• 我最近升级到了优胜美地。
• 当我安装 Xcode 时，我得到了 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。

我有一半希望这是编译器中的错误，否则这对我来说没有任何意义。非常感谢收到任何帮助!

最佳答案

我自己也在上斯坦福的类(class)，我也在这里卡了很长时间，但经过一番搜索，我从这里找到了一些东西:Xcode release notes它提到了以下内容:

Swift 1.2 is strict about checking type-based overloading of @objc methods and initializers, something not supported by Objective-C.

// Has the Objective-C selector "performOperation:".
func performOperation(op: NSOperation) { /* do something */ }
// Also has the selector "performOperation:".
func performOperation(fn: () -> Void) {
    self.performOperation(NSBlockOperation(block: fn))
}

This code would work when invoked from Swift, but could easily crash if invoked from Objective-C. To solve this problem, use a type that is not supported by Objective-C to prevent the Swift compiler from exposing the member to the Objective-C runtime:

• If it makes sense, mark the member as private to disable inference of @objc.
• Otherwise, use a dummy parameter with a default value, for example: _ nonobjc: () = (). (19826275)

Overrides of methods exposed to Objective-C in private subclasses are not inferred to be @objc, causing the Swift compiler to crash. Explicitly add the @objc attribute to any such overriding methods. (19935352)

Symbols from SDKs are not available when using Open Quickly in a project or workspace that uses Swift. (20349540)

我所做的只是在覆盖方法前添加“private”，如下所示:

    private func performOperation(operation: Double -> Double) {
    if operandStack.count >= 1 {
        displayValue = operation(operandStack.removeLast())
        enter()
    }
}

关于swift - 编译器错误 : Method with Objective-C selector conflicts with previous declaration with the same Objective-C selector，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/29457720/