Passing constructor with parameters to another constructor as argument-CodePudding

I have a struct Point, which has a constructor with parameters and a class called Circle.

struct Point{
    int x, y;
    Point(){}
    Point(int ox, int oy) : x(ox),y(oy){}
};

class Circle{
    public:
    Point obj;
    int radius;
    Circle(Point pt(int ox, int oy), int raza) : obj.x(ox), obj.y(oy), radius(raza) {}
};

int main()
{
    Circle(Point p(2,3),3);
    return 0;
}

The problem is that I don't know how to pass a struct constructor with parameters as parameter to my Circle class constructor.

CodePudding user response：

Circle(Point pt(int ox, int oy), int raza) : obj.x(ox), obj.y(oy), radius(raza) {}

is wrong syntax and should simply be:

Circle(Point pt, int raza) : obj(pt), radius(raza) {}

And then

Circle circle(Point(2, 3), 3);

CodePudding user response：

You can do that like this :

class Point
{
public:
    Point(int x, int y) :
        m_x(x),
        m_y(y)
    {
    }

private:
    int m_x{ 0 };
    int m_y{ 0 };
};

class Circle
{
public:
    Circle(const Point& pt, int raza) :
        m_point{ pt },
        m_radius{ raza }
    {
    }


private:
    Point m_point;
    int m_radius;

};

int main()
{
    Circle c1(Point(2,3), 3);

    // or use this shorter variant.
    // first parameter is a Point, {2,3} looks for a constructor 
    // of Point with two ints of point and finds it.
    Circle c2({ 2,3 }, 3);
    
    return 0;
}

CodePudding user response：

What you intended could be done in the following ways

Circle(int ox, int oy, int raza) : 
    obj(ox, oy)
    radius(raza) 
    {}

Circle(Point const& pt, int raza) :
    obj(pt), //note, here is the implicitly defined copy-constructor of obj called, not the one you defined
    radius(raza)
    {}

So If you define either of the constructors above the following will be valid

Circle        crl(1,2,3); //valid for the first constructor
Circle crl(Point(1,2),3); //valid for the second constructor
Circle    crl({1, 2}, 3); //valid for the second constructor