Working with Classes and Objects in C++

Introduction

In this C++ tutorial, we will learn about the fundamental concept of object-oriented programming, i.e., classes and objects. Classes are the blueprint of objects, and objects are instances of classes. We will understand the process of defining classes, creating objects, and manipulating these objects.

By the end of this tutorial, you will learn:
- What are classes and objects?
- How to define a class?
- How to create and use objects?

Prerequisites: Basic knowledge of C++ programming.

Step-by-Step Guide

Classes in C++

A class is a user-defined data type that we can use in our program, and it works as an object constructor, or a "blueprint" for creating objects. A class is defined using the keyword class, followed by the class name.

class ClassName {
  // class body
};

Objects in C++

An object is an instance of a class. When a class is defined, only the specification for the object is defined; no memory or storage is allocated. To use the data and access functions defined in the class, you need to create objects.

ClassName objectName;

Member Variables and Functions

A class contains both variables (attributes) and functions/methods.

class Car {
   public:
      string brand;   // attribute
      int year;  // attribute
      void honk() {   // method
         cout << "Beep beep!\n";
      }
};

Code Examples

Example 1: Creating a Class and an Object

#include <iostream>
#include <string>
using namespace std;

// Define a class
class Car {
   public:
      string brand;   
      int year;
};

int main() {
   // Create an object of Car
   Car carObj1;
   carObj1.brand = "Toyota";
   carObj1.year = 2015;

   // Access attributes and display the value
   cout << carObj1.brand << " " << carObj1.year << "\n";

   return 0;
}

In the above example, we first define a Car class with two attributes: brand and year. Then, we create an object carObj1 for the Car class and assign values to its attributes. Finally, we display these attribute values.

Expected Output: Toyota 2015

Summary

In this tutorial, we learned about classes and objects in C++. We defined a class using the class keyword and created objects to access the data members and functions. We also learned how to access these members and functions using the dot operator (.).

Next steps for learning include understanding concepts like constructors, destructors, and inheritance in C++. For additional resources, refer to C++ Documentation.

Practice Exercises

1. Exercise 1: Define a class Person with two attributes: name and age. Create an object of Person, set its attribute values and display them.

2. Exercise 2: Add a function birthday() to the Person class that increases the age by 1 when called. Create an object, increase its age using the function, and display its new age.

Solutions

1. Solution to Exercise 1

#include <iostream>
#include <string>
using namespace std;

// Define class Person
class Person {
   public:
      string name;   
      int age;
};

int main() {
   // Create an object of Person
   Person personObj;
   personObj.name = "John";
   personObj.age = 25;

   // Access attributes and display the value
   cout << personObj.name << " " << personObj.age << "\n";

   return 0;
}

1. Solution to Exercise 2

#include <iostream>
#include <string>
using namespace std;

// Define class Person
class Person {
   public:
      string name;   
      int age;
      void birthday() {
         age++;
      }
};

int main() {
   // Create an object of Person
   Person personObj;
   personObj.name = "John";
   personObj.age = 25;

   // Call birthday method
   personObj.birthday();

   // Access attributes and display the value
   cout << personObj.name << " " << personObj.age << "\n"; // Expect "John 26"

   return 0;
}

In the second exercise, we've added a birthday() function to the Person class that increases the age by 1 when it's called. We then called this function on our personObj to increase its age before displaying it.

Happy coding!