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OOP with C++ : Classes & Objects

OOP with C++: Classes & Objects

In C++ Object-Oriented Programming (OOP), classes act as blueprints for creating objects, which are individual instances of those blueprints. This concept forms the foundation of OOP, allowing you to model real-world entities and their behaviors within your code.

Understanding Classes:

  • A class defines the structure of its objects, including:
    • Data members: Variables representing the object's state or attributes (e.g., a car's model, year, color).
    • Member functions: Methods representing the object's behavior or actions (e.g., a car's start, stop, accelerate).
  • You can declare and define classes using the class keyword followed by the class name.

Creating Objects:

  • An object is an instance of a class, holding its own copy of data members and having access to member functions.
  • You create objects using the class name followed by the object name and a semicolon (;).
  • Example: Car myCar; creates an object named myCar of type Car.

Accessing Members:

  • Use the dot (.) operator to access an object's data members and member functions:
    • myCar.model = "Honda Civic"; sets the model data member of myCar.
    • myCar.start(); calls the start() member function of myCar.

Key OOP Concepts:

  • Encapsulation: Bundling data and methods together within a class, promoting data protection and hiding implementation details.
  • Inheritance: Creating new classes (subclasses) based on existing ones (superclasses), inheriting properties and potentially adding new ones.
  • Polymorphism: Enabling objects of different classes to respond to the same message in different ways, achieving flexible behavior.
  • Abstraction: Focusing on essential details and hiding complexity, creating reusable and easy-to-understand components.

Benefits of OOP:

  • Modular and organized code: Easier to understand, maintain, and reuse.
  • Realistic modeling: Objects represent real-world entities more naturally.
  • Flexibility and extensibility: Inheritance and polymorphism allow adapting code to new needs.
  • Data security: Encapsulation protects data integrity.

In C++, Object-Oriented Programming (OOP) is facilitated through classes and objects. Let's discuss classes and objects in C++:

Classes:

A class is a blueprint for creating objects. It defines the properties (data members) and behaviors (member functions) that objects of that class will have. Here's the basic syntax for defining a class in C++:

class ClassName { private: // Private data members and member functions protected: // Protected data members and member functions public: // Public data members and member functions };

Let's create a simple class called Person:

#include <iostream> #include <string> class Person { private: std::string name; int age; public: // Constructor Person(std::string n, int a) : name(n), age(a) {} // Member function to set name void setName(std::string n) { name = n; } // Member function to set age void setAge(int a) { age = a; } // Member function to display information void displayInfo() { std::cout << "Name: " << name << ", Age: " << age << std::endl; } };

Objects:

An object is an instance of a class. It represents a real-world entity that has attributes (data members) and behaviors (member functions) defined by its class. You can create multiple objects of the same class, each with its own set of data.

To create an object of a class, you use the class name followed by the object name and optional initialization parameters (if a constructor is defined):

ClassName objectName(initialization_parameters);

Using the Person class:

int main() { // Create objects of the Person class Person person1("Alice", 25); Person person2("Bob", 30); // Accessing member functions of objects person1.displayInfo(); person2.displayInfo(); // Modifying data members using member functions person1.setName("Charlie"); person1.setAge(35); person1.displayInfo(); return 0; }

Output:
Name: Alice, Age: 25
Name: Bob, Age: 30
Name: Charlie, Age: 35

In this example, Person is a class with data members name and age, along with member functions to set and display information. Two objects of the Person class (person1 and person2) are created, and their information is displayed using the member function displayInfo(). Then, the name and age of person1 are modified using the member functions setName() and setAge(), and the updated information is displayed.

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