c++ - Gtest，等于对象

Question

我想要等于 2 个对象，正好是卡片(使用 gtest 进行单元测试)。这是我的代码:

   #include "stdafx.h"
#include <gtest\gtest.h>
#include <vector>

class Card {
public:
    Card(int value, int color) :value(value), color(color) {};
    int returnColor() const { return color; };
    int returnValue() const { return value; };
    bool operator==(const Card &card) {
        return returnValue() == card.returnValue();
    };
private:
    int value;
    int color;
};

class CardTest : public ::testing::Test {
protected:
    std::vector<Card> cards;
    CardTest() { cards.push_back(Card(10, 2));
    cards.push_back(Card(10, 3));
    };
};
TEST_F(CardTest, firstTest)
{
    EXPECT_EQ(cards.at(0), cards.at(1));
}
int main(int argc, char *argv[])
{
    testing::InitGoogleTest(&argc, argv);
    return RUN_ALL_TESTS();
}

我有错误:

State Error C2678 binary '==': no operator found which takes a left-hand operand of type 'const Card' (or there is no acceptable conversion)

我尝试重载运算符“==”，但这不起作用:/也许，我必须走另一条路？这是我的第一个单元测试 :D。

Answer 1

相等运算符需要是const:

bool operator==(const Card &card) const {
                                  ^^^^^

有关 const 方法的讨论，请参阅 Meaning of "const" last in a C++ method declaration?