Runtime polymorphism in C++ - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a virtual function in the base class.

C++

class Base {
public:
    virtual void [1]() {
        std::cout << "Base function" << std::endl;
    }
};

Drag options to blanks, or click blank then click option'

Adisplay

Bshow

Cprint

Doutput

Attempts:

3 left

💡 Hint

Common Mistakes

Using a function name not matching the derived class function.

Forgetting to mark the function as virtual.

The function name display is used as the virtual function in the base class.

2fill in blank

medium

Complete the code to override the virtual function in the derived class.

C++

class Derived : public Base {
public:
    void [1]() override {
        std::cout << "Derived function" << std::endl;
    }
};

Drag options to blanks, or click blank then click option'

Aprint

Bshow

Cdisplay

Doutput

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different function name than the base class.

Omitting the override keyword.

The derived class overrides the display function declared virtual in the base class.

3fill in blank

hard

Fix the error in the code to call the derived class function through a base class pointer.

C++

Base* ptr = new Derived();
ptr->[1]();

Drag options to blanks, or click blank then click option'

Ashow

Bdisplay

Cprint

Doutput

Attempts:

3 left

💡 Hint

Common Mistakes

Calling a function name not declared in the base class.

Not using a pointer or reference to base class.

Calling display on the base class pointer invokes the derived class version due to virtual function.

4fill in blank

hard

Fill both blanks to define a base class pointer and call the virtual function.

C++

Base* [1] = new [2]();
[1]->display();

Drag options to blanks, or click blank then click option'

Aptr

BDerived

CBase

Dobj

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for pointer variable.

Creating an object of base class instead of derived.

The pointer ptr of type Base* points to a new Derived object to demonstrate runtime polymorphism.

5fill in blank

hard

Fill all three blanks to create a vector of base class pointers and call the virtual function on each.

C++

#include <vector>
#include <iostream>

std::vector<Base*> [1];
[1].push_back(new [2]());
[1].push_back(new [3]());

for (auto ptr : [1]) {
    ptr->display();
}

Drag options to blanks, or click blank then click option'

Aobjects

BDerived

CBase

Ditems

Attempts:

3 left

💡 Hint

Common Mistakes

Using different vector names in different places.

Adding base class objects instead of derived class objects.

The vector named objects holds pointers to Derived objects. Calling display on each pointer demonstrates runtime polymorphism.