class 指针的运算符重载无法正常工作

Question

我编写了一个非常简单的程序来尝试理解 C++ 中的运算符重载。然而，您也会看到，即使从运算符重载返回了适当的值，维度 d3 的结果也不会更新。

#include <iostream>

using namespace std;

class dimention{
    
protected:
    int width, height;
    
public:
    
    dimention(int w = 0, int h = 0){
        width = w;
        height = h;
    }
    
    int getWidth(){
        return width;
    }
    int getHeight(){
        return height;
    }

    dimention& operator = (const dimention &d){

        dimention *temp = new dimention;
        temp->height = d.height;
        temp->width = d.width;

        return *temp;
    }
    
    dimention& operator + (const dimention &d){
        
        dimention *newDimention = new dimention;
        
        newDimention->width = this->getWidth() + d.width;
        newDimention->height = this->getHeight() + d.height;

        return *newDimention;
    }
    
};

int main(){
    
    dimention *d1 = new dimention(5, 5);
    dimention *d2 = new dimention(1, 1);
    dimention *d3 = new dimention;

    *d3 = *d1;
    cout << d3->getHeight() << endl;
    cout << d3->getWidth() << endl;

    *d3 = *d1 + *d2;

    cout << d3->getHeight() << endl;
    cout << d3->getWidth() << endl;

    return 0;
}

感谢您的帮助。

Answer 1

我认为您误解了方法对对象的操作方式。

考虑赋值运算符：

dimention& operator = (const dimention &d){

    dimention *temp = new dimention;
    temp->height = d.height;
    temp->width = d.width;

    return *temp;
}

您永远不会编辑被分配给的对象本身 (this)。相反，您正在创建（并泄漏）一个新的 temp 对象并对其进行更改。该对象不是 d3.

正确的实施方式是：

dimention& operator = (const dimention &d){
    this->height = d.height;
    this->width = d.width;
    return *this;
}

会给你预期的结果。

class 指针的运算符重载无法正常工作

Operator overloading not working as intended for class pointers

c++

operator-overloading

operators