Class factory to create derived classes c++ - c++

Question

I'm currently learning about class factory patterns with C++. I keep having errors while trying to implement the factory. Suppose I have an abstract class and two derived classes. What I want the factory to do is to create a new object of the base class like so: Ball *sc = new SoccerBall();
I am not sure on how to implement this, I have tried but of no avail. What do I need to fix?
class Ball
{
public:
Ball();
virtual ~Ball();
virtual int getSize() const = 0;
virtual void setBallSize(int s) = 0;
virtual string ballManufacturer() const = 0;
protected:
int ballSize;
}
class Soccerball:public Ball
{
public:
Soccerball();
Soccerball(int size);
~Soccerball();
int getSize() const;
void setBallSize(int s);
string ballManufacturer() const;
}
class Soccerball:public Ball
{
public:
Soccerball();
Soccerball(int size);
~Soccerball();
int getSize() const;
void setBallSize(int s);
string ballManufacturer() const;
}
class Basketball:public Ball
{
public:
Basketball();
Basketball(int size);
~Basketball();
int getSize() const;
void setBallSize(int s);
string ballManufacturer() const;
}
class BallFactory
{
public:
Ball* createBall(string s)
{
if(s == "Soccer")
{
return new Soccerball(5);
}
if(s == "Basket")
{
return new Basketball(6);
}
}
}

Answer 1

This how your code will work, but above when you are posting a question you should provide "Short Self Contained Correct Code" and make easy for people to understand your problem easily.
#include <iostream>
using namespace std;
class Ball
{
public:
Ball()
{
cout<<"Ball ctr"<<endl;
}
virtual ~Ball()
{
}
virtual int getSize() const = 0;
virtual void setBallSize(int s) = 0;
virtual string ballManufacturer() const = 0;
protected:
int ballSize;
};
class Soccerball:public Ball
{
public:
Soccerball()
{
cout<<"create Default Soccer Ball "<<endl;
}
Soccerball(int size)
{
cout<<"create Soccer Ball "<<size<<endl;
}
~Soccerball()
{
}
int getSize() const
{
return ballSize;
}
void setBallSize(int s)
{
ballSize = s;
}
string ballManufacturer() const
{
return "";
}
};
class Basketball:public Ball
{
public:
Basketball()
{
cout<<"create default Baseket Ball "<<endl;
}
Basketball(int size)
{
cout<<"create Baseket Ball "<<size<<endl;
}
~Basketball()
{
}
int getSize() const
{
return ballSize;
}
void setBallSize(int s)
{
ballSize = s;
}
string ballManufacturer() const
{
return "";
}
};
class BallFactory
{
public:
//Factory method
static Ball* createBall(string s)
{
if(s == "Soccer")
{
return new Soccerball(5);
}
if(s == "Basket")
{
return new Basketball(6);
}
}
};
int main()
{
Ball* ptr = BallFactory::createBall("Soccer");
return 0;
}
But you also need to understand how Factory design pattern works and how a namesake virtual constructor is created and why you would use a parameterized factory. Or could you use a template factory.