19. Object-oriented programming: basic concepts

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Object-Oriented Programming (OOP) is a programming paradigm that uses abstraction to create models based on the real world. It utilizes several previous programming techniques, including inheritance, polymorphism, abstraction, and encapsulation. Today, many popular programming languages ​​(such as Java, JavaScript, C#, C++, Python, PHP, Ruby, and Objective-C) support object-oriented programming (OOP).

The basic concepts of OOP are:

Objects

Objects are an instance of a class where the class can be seen as a blueprint while objects are a copy of the blueprint. For example, if the class is a car model, then one object would be a Ferrari, another object would be a BMW, etc. Objects are composed of states and behaviors.

Classes

A class is a blueprint or set of instructions for creating a specific object. It defines the variables and methods (functions) that the object created from the class will contain. For example, the Car class could include variables like model, color, year, and methods like drive, stop, etc.

Inheritance

Inheritance is a mechanism that allows a class to inherit properties and behaviors from a parent class. This helps promote code reuse and business logic. For example, if we have a Car class with properties like color and methods like Stop, and we want to create a new Ferrari class, we can make Ferrari inherit all the properties and methods from the Car class and only add those properties and methods that are unique to the Car class. Ferrari.

Polymorphism

Polymorphism is the principle by which we can use a single interface to represent different kinds of things. A classic example of polymorphism is the draw function on different objects such as circles, rectangles and triangles. Each of these objects would have a different implementation of the draw function, but you could invoke the draw function on any of these objects without knowing what class the object belongs to, and they would behave correctly.

Abstraction

Abstraction is a process of hiding implementation details and showing only functionality to users. In other words, the user only interacts with what is necessary, while the internal details are hidden. For example, when driving a car, you don't need to know how the engine or brake system works. You just need to know how to use the controls like the steering wheel, pedals, etc.

Encapsulation

Encapsulation is a concept that implies encapsulating all properties and methods within a class and hiding the implementation details from the user. It creates a black box and protects the object's data from direct access, which is a way to reduce complexity and increase reusability.

In summary, Object Oriented Programming is a style of programming that is encapsulated around objects and data, rather than functions and logic. An important feature of object-oriented programming is the division of programs into smaller parts or objects to make software development more manageable, flexible, and modular.

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2020. Classes and Objects