Operator overloading not working as intended for class pointers-CodePudding

I've made a very simple program trying to understand operator overloading in C . However as you too will see, the result of the dimention d3 is not updated even though the appropriate values are returned from the operator overloading.

#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;
}

Thanks for your help.

CodePudding user response：

I think you misunderstand the way methods operate on an object.

Consider the assignment operator:

dimention& operator = (const dimention &d){

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

    return *temp;
}

You are never editing the object itself (this) that is being assigned to. Instead, you are creating (and leaking) a new temp object and changing it. That object is not d3.

A correct implementation would be:

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

Same here:

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

Will give you the expected result.