c++ - enum 类型不能接受 cin 命令

Question

请看这段代码：

#include <iostream>
using namespace std;
int main()
{

    enum object {s,k,g};
    object o,t;

    cout << "Player One: "; cin >> o;
    cout << "Player Two: "; cin >> t;

    if (o==s && t==g) cout << "The Winner is Player One.\n";
    else if (o==k && t==s) cout << "The Winner is Player One.\n";
    else if (o==g && t==k) cout << "The Winner is Player One.\n";
    else if (o==g && t==s) cout << "The Winner is Player Two.\n";
    else if (o==s && t==k) cout << "The Winner is Player Two.\n";
    else if (o==k && t==g) cout << "The Winner is Player Two.\n";
    else cout << "No One is the Winner.\n";
        return 0;
}

在编译时我会得到这个错误：no match for 'operator>>' in 'std::cin >> o 我正在使用代码块。那么这段代码有什么问题呢？

Answer 1

枚举没有运算符>>()。您可以自己实现一个：

std::istream& operator>>( std::istream& is, object& i )
{
    int tmp ;
    if ( is >> tmp )
        i = static_cast<object>( tmp ) ;
    return is ;
}

当然，如果你只是 cin 一个整数并自己转换会更容易。只想向您展示如何编写 cin >> 运算符。

Answer 2

您是否希望能够输入“s”、“k”或“g”并将其解析为您的枚举类型？如果是这样，您需要定义自己的流运算符，如下所示：

std::istream& operator>>(std::istream& is, object& obj) {
    std::string text;
    if (is >> text) {
        if (text == "s") {
            obj = s;
        }
        // TODO: else-if blocks for other values
        // TODO: else block to set the stream state to failed
    }
    return is;
}

Answer 3

如果您不熟悉运算符重载概念并想要快速修复，只需使用：

scanf("%d%d", &o, &t);