Shape drawings

Create a base class Shape with a method draw() that outputs "Drawing a generic shape." Create a derived class Circle that overrides the draw() method to output "Drawing a circle."

Create a Shape pointer and make it point to a Circle object.
Call the draw() method using this pointer.
Observe and explain the output.

Hint

Remember that the method called is determined by the type of the pointer, not the type of the object it points to.

Answer

#include <iostream>

class Shape {
public:
    void draw() {
        std::cout << "Drawing a generic shape." << std::endl;
    }
};

class Circle : public Shape {
public:
    void draw() {
        std::cout << "Drawing a circle." << std::endl;
    }
};

int main() {
    Shape* shapePtr = new Circle();
    shapePtr->draw();  // Output will be "Drawing a generic shape."
  
    delete shapePtr;  // Clean up memory
    return 0;
}

Explanation: The draw() method from the Shape class is called because the pointer shapePtr is of type Shape*, even though it points to a Circle object.

Part 2

Using the code you just created, cast shapePtr to a Circle* before calling draw from it and observe the difference.

Part 2 Answer

int main() {
    Shape* shapePtr = new Circle();
    shapePtr->draw();  // Output will be "Drawing a generic shape."
  
    delete shapePtr;  // Clean up memory
    return 0;
}

Because draw is called from a Cicle pointer, it calls Circle::draw.

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