当我只返回对象c ++的引用时，为什么调用复制构造函数

Question

It is the code which I cannot figure out why it is not working the way I want, I look around the internet, but did not some good solution.

Point class:

class Point
{
public:
    Point(const Point &) {
        cout << "copy constructor was called" << endl;
    }
    Point(int x, int y) : x(x), y(y) {
    }
    void setX(int x) {this->x = x;}
    void setY(int y) {this->y = y;}
    int getX() const { return x; }
    int getY() const  { return y; }
private:
    int x;
    int y;
};

Circle class:

class Circle
{
private:
    int rad;
    Point &location;
public:
    Circle(int radius, Point &location) : rad(radius), location(location) {}
    int getRad() { return rad; }
    Point & getLocation() { return location; }
};

The usage:

int main() {
    Point p(23, 23);
    Circle c(12, p);

    Point p1 = c.getLocation();
    p1.setX(200);

    cout << p.getX() << endl; // prints 23, which I want to be 200
                              // copy constructor was called

    system("pause");
    return 0;
}

Answer 1

In the following line:

Point p1 = c.getLocation();

p1 is not a reference, so basically you're copying the referenced object returned by getLocation() , thus calling copy constructor.

A solution would be to declare p1 as a reference like this:

Point& p1 = c.getLocation();