Factory Pattern Sample

C++ DesignPattern OOP

Source Code

#include <iostream>
#include <string>
using namespace std;
class Shape{
    public:
    virtual void Draw() {};
};
class Circle : public Shape{
    void Draw(){ cout<<"Draw a circle"<<endl; }
};
class Square : public Shape{
    void Draw(){ cout<<"Draw a square"<<endl;  }
};
class Rectangle : public Shape{
    void Draw(){ cout<<"Draw a rectangle"<<endl;  }
};
class Triangle : public Shape{
    void Draw(){ cout<<"Draw a triangle"<<endl;  }
};
class Casual : public Shape{
    void Draw(){ cout<<"Draw casually"<<endl;  }
};
class ShapeFactory{
    public:
    static Shape* Relshape(string type) {
        if(!type.compare("CIRCLE")) {
            return new Circle(); 
        } else if(!type.compare("SQUARE")) {
            return new Square(); 
        } else if(!type.compare("RECTANGLE")) {
            return new Rectangle();
        } else if(!type.compare("TRIANGLE")) {
            return new Triangle();
        } else {
            return new Casual();
        }
    }
};
class FactoryPattern{
public:
    FactoryPattern(){
        cout<<"************MENU*************"<<endl;
        cout<<"*** 1.CirCle              ***"<<endl;
        cout<<"*** 2.Square              ***"<<endl;
        cout<<"*** 3.Rectangle           ***"<<endl;
        cout<<"*** 4.Triangle            ***"<<endl;
        cout<<"*** 5.Casually            ***"<<endl;
        cout<<"*****************************"<<endl;
        cout<<"FactoryPattern------What do you want to draw?"<<endl;
        cout<<"Answer-----  ";
        cin>>tag;
        switch(tag)
        {
            case 1:shape= ShapeFactory::Relshape("CIRCLE"); break;
            case 2:shape= ShapeFactory::Relshape("SQUARE"); break;
            case 3:shape= ShapeFactory::Relshape("RECTANGLE");  break;
            case 4:shape= ShapeFactory::Relshape("TRIANGLE");   break;
            default:shape= ShapeFactory::Relshape("");  break;
        }
        shape->Draw();
    }
    ~FactoryPattern(){}
private:
    int tag;
    Shape* shape;
};
int main()
{
    FactoryPattern factory;
    return 0;
}

Debug

1. error : expected '}' at end of input
   reason : lose matching '}'
   solution : check all {} one by one
2. error : could not convert '……' from 'Circle*' to 'Shape'
   reason : type matching failed
   solution : check the return-value and return-type of the function and assignment variables' type
3. error : "……" is private within this context
   reason : lose the tag "public:" in class
4. error : undefined reference to `vtable for Shape'
   reason : undefined reference stands failure in process of link, 'vtable' is created by virtual interface class, this error stands the definition has not been implemented
   solution : "virtual void Draw();" -> "virtual void Draw() {};"

tips:
new class should be defined with () , e.g. new Cirle()