CODEWITHSUNDEEP
c++polymorphismstatic-polymorphism
Steve
Steve

Reputation: 849

How to in C++ substitute the dynamic polymorphism by the static one?

Let's say I have following code exploiting the dynamic polymorphism in C++

GraphicalObject.h

class GraphicalObject
{
public:
    virtual void draw() = 0;
};

Rectangle.h

#include "GraphicalObject.h"

class Rectangle : public GraphicalObject
{
    void draw();
};

Rectangle.cpp

#include "Rectangle.h"
#include <iostream>

void Rectangle::draw() {
    std::cout << "Drawing rectangle!" << std::endl;
}

Circle.h

#include "GraphicalObject.h"

class Circle : public GraphicalObject
{
    void draw();
};

Circle.cpp

#include "Circle.h"
#include <iostream>

void Circle::draw() {
    std::cout << "Drawing circle!" << std::endl;
}

main

int main(int argc, char** argv) {

    Rectangle rectangle;
    Circle circle;

    GraphicalObject* picture[2];
    
    picture[0] = &rectangle;
    picture[1] = &circle;
    
    for(GraphicalObject* o : picture) {
        o->draw();
    }
    
    return 0;
}

My question is whether there is a possibility how to have the picture array without dynamic polymorphism and instead of use only the static polymorphism and avoid the virtual method? The reason why I would like to avoid the virtual method is that I would like to avoid the overhead related to the access into the vtable.

Upvotes: 0

Views: 123

Answers (1)

Swift - Friday Pie
Swift - Friday Pie

Reputation: 14589

The problem here is that objects pointed by GraphicalObject* picture[2]; got static type GraphicalObject and static polymorphism uses static type.

But that doesn't mean static polymorphism isn't possible is similar situation. You would need a wrapper class which would know the actual type of stored object and would cast the pointer to it before calling the methods.

Upvotes: 1

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