Explore classes and object-oriented programming concepts like information-hiding, inheritance, and polymorphism.

Become a C++ Programmer

In this module, we’ll dive into understanding the time-honored technique for implementing complex applications using user-defined classes. Moreover, we’ll discuss classes and objects, then build up to the high-level topics including inheritance and polymorphism.

Throughout the module, we’ll work with OOP for C++, with illustrations, exercises, quizzes, and hands-on challenges. By end of this module, we’ll have an understanding of classes and objects' behavior and be able to easily create simple, efficient, reusable, and secure code.

Object-oriented Programming in C++

Member initializer list allows us to initialize data members of an object without writing assignment statements in a constructor. Without further ado, here is an example:

#include <iostream>
#define PI 3.1416
using namespace std;

class Sphere {
  private: 
    const double density;
    double radius;
  public:
    Sphere(double r) : radius(r), density(4.3) {
      // The following initialization wouldn't work, because density is a const
      // density =  4.3;
    }
    double volume() {
      return 4 * PI * radius * radius * radius / 3;
    }
    double mass() {
      return density * volume();
    }
};
int main() {
  // your code goes here
  Sphere s(3.2);
  cout << "Volume: " << s.volume() << ", mass: " << s.mass();
  return 0;
}

Our `Sphere` class stores the `radius` and `density` of a sphere. We have defined functions to obtain the volume and mass of the sphere. The constructor uses member initializer list on line $10$ to initialize the member variables. 

Inside `main()`, we declare a `Sphere`  object with radius $3.2$ on line $23$ and then displayed its volume and mass on line $24$.

One advantage of member initializer list is that it makes things compact. One no longer has to use assignment statements in the constructor. Another important point is that any `const` class members can't be initialized inside a constructor and must be initialized using member initializer lists.

Learn about member initializer lists in C++

Introduction

Classes

Data Hiding

Inheritance

Polymorphism

Composition, Aggregation and Association

Conclusion

Member Initializer Lists