MSDN Documentation - Concepts: Classes

Classes

Classes are fundamental building blocks in object-oriented programming (OOP). They serve as blueprints for creating objects, encapsulating data (properties or fields) and behavior (methods or functions) that operate on that data.

What is a Class?

A class defines the structure and behavior of a type of object. Think of it as a template. When you create an object from a class, it's called an instance of that class.

Key Components of a Class

Properties (or Fields): These represent the data or state associated with an object. For example, a Car class might have properties like color, model, and year.
Methods (or Functions): These define the actions or behaviors that an object can perform. For the Car class, methods might include startEngine(), accelerate(), or brake().
Constructor: A special method that is automatically called when an object is created from a class. It's typically used to initialize the object's properties.

Creating a Class

The syntax for defining a class varies slightly between programming languages, but the core concept remains the same. Here's a conceptual example:


class Vehicle {
    // Properties
    string color;
    string model;
    int year;

    // Constructor
    Vehicle(string color, string model, int year) {
        this.color = color;
        this.model = model;
        this.year = year;
    }

    // Method
    void startEngine() {
        print("Engine started for " + this.model);
    }

    // Method
    string getDescription() {
        return this.year + " " + this.color + " " + this.model;
    }
}

Instantiating Objects (Creating Instances)

Once a class is defined, you can create objects from it. This process is called instantiation.

Example Usage:


// Create an instance of the Vehicle class
Vehicle myCar = new Vehicle("Red", "Sedan", 2023);

// Access properties
print(myCar.color); // Output: Red
print(myCar.model); // Output: Sedan

// Call methods
myCar.startEngine(); // Output: Engine started for Sedan
print(myCar.getDescription()); // Output: 2023 Red Sedan

Benefits of Using Classes

Encapsulation:: Bundling data and methods that operate on the data within a single unit (the class). This helps in organizing code and controlling access to data.
Reusability:: Classes can be reused across different parts of an application or in multiple projects, saving development time.
Abstraction:: Classes allow you to hide complex implementation details and expose only the necessary functionalities to the outside world.
Maintainability:: Well-defined classes make code easier to understand, debug, and modify.