正确编写引用的比较运算符

Question

我有代码：

#include <vector>

#define DECK_SIZE 52

struct Card {
    int Value;
    int Suit;

    bool operator == (Card &c1) {
        return ((Value == c1.Value) && (Suit == c1.Suit));
    }
};

typedef std::vector<Card> hand_t;

bool IsCardInHand(const Card & checkCard, const hand_t & hand)
{
    for (int i = 0; i < static_cast<int>(hand.size()); ++i) {
        if (checkCard == hand[i]) {
            return true;
        }
    }

    return false;
}

此行：if (checkCard == hand[i]) 生成错误：IntelliSense 的 IntelliSense: no operator "==" matches these operands 和编译器 (Visual C++ 2010) 的 error C2678: binary '==' : no operator found which takes a left-hand operand of type 'const Card' (or there is no acceptable conversion)。

请帮忙，我怎样才能正确重写 operator==？

Answer 1

你需要（注意常量）：

bool operator == (const Card &c1) const {

正确编写引用的比较运算符

Correctly write comparison operator for references

c++

reference

pass-by-reference