一元运算符++不能应用于Int类型的操作数 [英] Unary operator ++ cannot be applied to an operand of type Int

问题描述

为什么下面的快速代码给我带来错误一元运算符'++'不能应用于'Int'类型的操作数??? （在Xcode-6.3.2上使用swift-1.2）

Why does the following swift code bring me the error "Unary operator '++' cannot be applied to an operand of type 'Int'" ??? (using swift-1.2 on Xcode-6.3.2)

struct Set {

    var player1Games: Int
    var player2Games: Int

    init() {
        self.player1Games = 0
        self.player2Games = 0
    }

    func increasePlayer1GameScore () {
        player1Games++   // error: Unary operator '++' cannot be applied to an operand of type 'Int'
    }

    func increasePlayer2GameScore () {
        player2Games++   // error: Unary operator '++' cannot be applied to an operand of type 'Int'
    }

}

推荐答案

错误消息有点误导。您需要做的是在 func 之前添加变异以指定它将修改结构：

The error message is a bit misleading. What you need to do is add mutating before func to specify that it will modify the struct:

struct MySet {

    var player1Games: Int
    var player2Games: Int

    init() {
        self.player1Games = 0
        self.player2Games = 0
    }

    mutating func increasePlayer1GameScore() {
        player1Games++
    }

    mutating func increasePlayer2GameScore() {
        player2Games++
    }

}

注意： Set 是Swift中的一个类型，我建议为你的结构使用不同的名称。

Note: Set is a type in Swift, I would suggest to use a different name for your struct.

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