What is Class in Object Oriented Programming?

What is a Class in OOP?

Classes are the building blocks of OOP in the realm of C++. It's similar to creating a prototype for a certain sort of object, encapsulating its attributes (data) and methods (functions) that operate on that data. They enable you to simulate real-world entities, abstract notions, or any aspect of your issue area. Assume you're creating a virtual zoo program. You'd construct a Animal class with attributes such as name, species, and age, as well as actions such as eat, sleep, and makeSound.

Encapsulation is a crucial aspect of object-oriented programming that ensures data integrity and enhances code security. By encapsulating data within classes and controlling access to it through methods, sensitive information can be protected and manipulated in a controlled manner.

Here's an example that highlights the importance of encapsulation and demonstrates how private attributes are accessed through public methods, using C++ as the programming language:

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In this example, the BankAccount class encapsulates sensitive data like the account number and balance. Private attributes such as accountNumber and balance are accessed by public getter methods getAccountNumber() and getBalance(). This encapsulation allows controlled access to the data and maintains its integrity by preventing unauthorized modifications.

Creating a Class

Creating a class in C++ involves a few key steps. You begin by declaring the class with the class keyword, followed by the class name. Then, inside the curly brackets, declare the member variables (attributes) that indicate the object's state. Integers, strings, and more complicated data structures can be used.

Following that, you define member functions that operate on the class data. These functions can alter data, give functionality, and interact with other objects. For example, in your Animal class, you could include a function that calculates an animal's species' remaining years till retirement.

C++ classes offer access modifiers such as public, private, and protected. These determine how visible and accessible class members are.

Public members can be accessed from outside the class, secret members can only be accessed from within the class, and protected members fall somewhere in the centre.

Example:

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Let us take another example that demonstrates how different classes can implement the same method name to achieve dynamic behavior using polymorphism:

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In the above example:

• The Shape class defines a virtual method draw() which serves as a blueprint for drawing shapes.
• The Circle, Square, and Triangle classes inherit from Shape and override the draw() method with their specific implementations.
• In the main() function, an array of pointers to Shape objects is created, each pointing to an instance of a different derived class (Circle, Square, and Triangle).
• The for loop iterates through the array and calls the draw() method on each object. Despite the method being the same name, the dynamic behavior of polymorphism ensures that the correct implementation based on the object's actual type is invoked.

Components of a Class

A class in programming is a blueprint for constructing objects, encapsulating both data and the methods for manipulating it. Understanding a class's components is critical for designing efficient and well-organized code.

• Attributes: Also known as properties, attributes are variables that contain class-specific data. These can range from simple numbers to complicated data structures.
• Methods: Methods are the functions that define the behavior of a class. They allow attribute interaction and can conduct actions or return information.
• Constructor: The constructor method initializes the class object. It is run whenever a new object is formed and assigns initial values to attributes.
• Inheritance: This feature allows a class to inherit characteristics and methods from another class, promoting reuse and code hierarchy.
• Encapsulation: Encapsulation limits direct access to attributes, which promotes data integrity. Public, private, and protected access modifiers control visibility and manipulation.
• Polymorphism: Polymorphism is a fascinating characteristic of classes that allows objects of various classes to be considered objects of a shared parent class, increasing versatility.

What is an Object?

An object is a self-contained unit that combines data (attributes) and functions that operate on that data (methods). Consider objects to be real-world objects having traits and behaviors. Consider the Car object as an example. Its characteristics could include things like colour, make, and model, while its methods could include things like startEngine() and accelerate(). This method assists developers in organizing their code more understandably, allowing for greater abstraction, reusability, and maintainability.

Declaring the Objects

Declaring an object entails naming and declaring its type. In C++, this is often accomplished through a class or struct declaration. To make a Student object, for example, you would construct a class called Student with attributes like name, age, and methods like study() and takeExam(). After you've defined the class, you can declare instances of it by using the class name and an identifier.

Initializing and Using the Objects

Once an object is declared, it must be initialized before it can be used. This entails giving value to its characteristics. Constructors are used to initialise objects in C++. You might create a constructor for our Car object that takes arguments like color, make, and model and initializes the attributes accordingly.

After initialization, you can access an object's attributes and methods using the dot notation. For example, if you have a Student object named alice, you may set her age with alice.age = 20 and use her study() method with alice.study().

Example:

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Use Cases of Objects and Classes in OOPs

Let's look at some examples of how objects and classes are used.

• Modularity and Encapsulation: Classes encapsulate data and methods, promoting modular design. This protects internal intricacies, making maintenance and updates easier. Consider a banking application. Instead of having all the banking-related functions scattered throughout the code, you can create a BankAccount class that encapsulates methods like deposit, withdraw, and getBalance. This modular design protects the inner workings of these methods and allows for easier maintenance and updates.
• Code Reusability: Objects can be reused between projects, reducing redundancy. This speeds up development while also ensuring codebase consistency. Imagine you're working on a project that involves different types of vehicles. Instead of writing separate code for each vehicle type, you can create a base Vehicle class with common attributes and methods like start, stop, and getSpeed. Then, you can derive specialized classes like Car, Motorcycle, and Truck from the Vehicle class, inheriting its properties and methods.
• Inheritance: Classes can inherit properties and methods from other classes, creating a hierarchical structure. This simplifies code management and promotes the development of specialized classes. Building upon the vehicle example, let's say you have a Car class. You can inherit properties like start and stop from the base Vehicle class. Additionally, you can add specialized methods like openTrunk and turnOnAC specific to cars. This hierarchical structure simplifies code management, ensures consistent behavior across different vehicle types, and allows for the efficient development of new vehicle classes.
• Polymorphism: Different classes can implement the same method name, allowing for dynamic behavior depending on the kind of object. This encourages code that is flexible and expandable. Continuing with vehicles, consider the concept of a Race where different types of vehicles participate. Each vehicle type can have its implementation of a race() method. During the race, you can call the race() method on each vehicle without worrying about the specific type. This dynamic behavior allows you to extend the race to include new vehicle types without modifying existing code.
• Abstraction: Classes can abstract complex functions, revealing only useful characteristics to consumers. This simplifies interaction with the code and reduces the possibility of errors. For example, let's say you're creating a simulation of a zoo. You can abstract the concept of an animal into an Animal class with methods like eat, sleep, and makeSound. Concrete animal classes like Lion, Elephant, and Giraffe can then inherit from Animal. Consumers of the code interact with the high-level Animal interface, simplifying interactions and shielding them from the complexities of individual animal implementations.
• Real-world Modelling: Objects represent real-world entities, improving the mapping of real-world circumstances to code. This allows for more precise problem-solving and improves communication between engineers and domain experts. Suppose you're building a medical application to manage patient records. Instead of directly dealing with low-level database operations, you can create a Patient class that represents a patient's attributes like name, age, and medical history. This abstraction enhances the mapping of real-world patients to code, making the application more intuitive and easier to understand for both developers and medical professionals.
• Collaborative Development: Classes enable many developers to work on different portions of the application simultaneously, encouraging parallel development and reducing conflicts. Imagine a team developing a video game. Different developers can work on various aspects, such as characters, enemies, and game mechanics, by creating separate classes. These classes can then be integrated into the game seamlessly, enabling parallel development and minimizing conflicts.
• Testing and Debugging: Isolating objects makes testing and debugging more efficient because errors within encapsulated units are easier to spot. Suppose you're developing a software application with multiple modules. If an issue arises in a specific module, isolating the problem is easier if the code is organized into classes. For example, if there's a bug in the Payment module, you can focus your debugging efforts on the Payment class, making the process more efficient.