C++ 中的运算符重载：不合格 ID 错误 [重复]

Question

我们刚开始在我的计算模块中学习类和运算符重载，我对给出的示例之一有疑问：

 #include <iostream>
using namespace std;

int main()
{
    class PositivePoint
    {
        // Must return PositivePoint object by value
        PositivePoint operator+(const PositivePoint& pSrc);
    };

    PositivePoint PositivePoint::operator+(const PositivePoint& pSrc)
    {
        Positive Point ret;
        ret.mX = mX + pSrc.mX;
        ret.mY = mY + pSrc.mY;
        return ret;
    }

    // Return success
    return 0;
}

我不断收到错误“unqualified-id in declaration before '(' token。我不明白为什么会这样，因为我认为在上面的示例中正确定义了运算符重载。

Answer 1

您的代码几乎没问题，至少在运算符的语法上是这样。 您需要将类和运算符移出主要功能... 定义 mX, My 并更正为 ret 声明的错字

在那之后我测试并工作了......

#include <iostream>
using namespace std;
class PositivePoint {
public:
    int mY;
    int mX;
    // Must return PositivePoint object by value
    PositivePoint operator+(const PositivePoint& pSrc);
};

PositivePoint PositivePoint::operator+(const PositivePoint& pSrc) {
    PositivePoint ret;
    ret.mX = mX + pSrc.mX;
    et.mY = mY + pSrc.mY;
    return ret;
}

int main() {
    PositivePoint a;
    a.mX = 1;
    a.mY = -2;
    
    PositivePoint b;
    b.mX = 3;
    b.mY = 5;
    
    PositivePoint c = a + b;
    std::cout << "Hello World!"<< std::endl;
    std::cout << "c.X: " << c.mX << std::endl;
    std::cout << "c.Y: " << c.mY << std::endl;
 
    // your code goes here
    return 0;
}