重写Swift中的func [英] Overriding func in Swift

问题描述

我正在学习Swift，并且我正在按照Paul Hegarty的一篇教程介绍如何使用波形反转表示法来构建计算器。代码如下所示：

  @IBAction func操作（sender：UIButton）{
 let operation = sender.currentTitle ！ 
 if userIsEnteringData {
 enter（）
} 
开关操作{
 case×：performOperation {$ 0 * $ 1} 
 case÷： performOperation {$ 1 / $ 0} 
 case+：performOperation {$ 0 + $ 1} 
 case - ：performOperation {$ 1  -  $ 0} 
 case√：performOperation {sqrt（$ 0 ）} 
 casesin：performOperation {sin（$ 0）} 
 casecos：performOperation {cos（$ 0）} 
 caseπ：performOperation {$ 0 * M_PI} 
 default：break 
} 
 
} 
 
 func performOperation（操作：（Double，Double） - &Double; Double）{
 $ b （b）如果operandStack.count> = 2 {
 displayValue = operation（operandStack.removeLast（），operandStack.removeLast（））
 enter（）
 
 
} 
 
 func performOperation（操作：Double  - > Double）{
 
如果operandStack.count> = 1 {
 displayValue = operation（operandStack.removeLast （））
输入（）
 
 } 
} 
  

xCode编译器不喜欢performOperation函数和报告的第二个实例它以前已经定义过。它报告的错误是：使用Objective-C选择器'performOperation：'的方法'performOperation'与之前的声明冲突，使用相同的Objective-C选择器

我的代码有什么问题？

解决方案

我不知道你的类声明，但在这种情况下最可能的问题是你从 @objc 类。 Objective-C不支持方法重载，但Swift的确如此。因此，如果可以的话，您不应该继承 @objc 类，或者您可以使用不同的方法名。

参考你可以阅读这篇文章

I am learning Swift and I am following a tutorial from Paul Hegarty on how to build a calculator using Polish Inverse Notation. The code looks like this:

@IBAction func operate(sender: UIButton) {
    let operation = sender.currentTitle!
    if userIsEnteringData{
        enter()
    }
    switch operation {
    case "×": performOperation {$0 * $1}
    case "÷": performOperation {$1 / $0}
    case "+": performOperation {$0 + $1}
    case "−": performOperation {$1 - $0}
    case "√": performOperation {sqrt($0)}
    case "sin": performOperation {sin($0)}
    case "cos": performOperation {cos($0)}
    case "π": performOperation{$0 * M_PI}
    default: break
    }

}

func performOperation (operation : ( Double, Double ) -> Double){

    if operandStack.count >= 2 {
        displayValue = operation(operandStack.removeLast(), operandStack.removeLast())
        enter()

    }
}

func performOperation (operation : Double -> Double){

    if operandStack.count >= 1 {
        displayValue = operation(operandStack.removeLast())
        enter()

    }
}

The xCode compiler does not like the second instance of the performOperation function and reports that it has already been defined previously. The error it reports is:

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

What is wrong with my code?

解决方案

I am not aware of your class declaration but the most possible issue in this case is that you inherit from an @objc class. Objective-C does not support method overloading but Swift does. So either you shouldn't be inheriting from am @objc class if you can or you can just use different method names.

For reference you can read this post

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