Understanding Object-Oriented Programming

Just like many of us, I began my coding journey with procedural programming. It’s like learning the basics of handling a bicycle before even thinking about a motorcycle. It’s straightforward and logical, making it an excellent starting point for anyone new to programming. However, as you progress and your projects become more complex, you’ll inevitably encounter the need for a more sophisticated toolset – that’s where Object-Oriented Programming (OOP) comes into play.

What is OOP?

It is a paradigm that consists of modeling a problem with a set of objects:

OOP ≡ (SET OF OBJECTS AND THE INTERACTIONS BETWEEN THESE OBJECTS)

• An object represents a concept, an idea, or any entity from the physical world (a car, a person, or even a page of a book).
• OOP is easily conceivable because it describes entities as they exist in the real world.
• The program is built around objects that combine data (attributes) and actions (methods).

Advantages of OOP: ease of organization, reusability, inheritance capability, ease of correction, easier to manage projects.

• OOP allows securing a program by either allowing or prohibiting access to these objects by other parts of the program.

What is an Object?

It is a data structure responsible for managing data, organizing it, and storing it in a certain form:

OBJECT ≡ IDENTITY + STATE (attributes) + BEHAVIOR (member methods)

• Identity: An object has an identity that allows it to be distinguished from other objects, regardless of its state.

• Attributes: These are the data characterizing the object. They are variables that store information about the object’s state.

• Methods (member functions): An object’s methods characterize its behavior, i.e., the set of actions that allow:

  • To consult, modify, etc.… the object’s state (the values of the attributes),
  • To communicate with other objects by sending messages to perform a process…

• Communications between objects are synchronous: The calling object waits for a response before being able to do something else.

What is a Class?

Objects of the same nature belong to the same family called Class:

CLASS ≡ (Abstraction of a set of objects sharing a common structure and common behavior)

CLASS ≡ INSTANTIATION + ATTRIBUTES (instance variables) + MEMBER METHODS

• Instantiation: represents the relationship between an object and its belonging class that allowed its creation.
• Attributes (also called instance variables): They have a name and a type: either a basic type (simple or constructed), or a class (the attribute references an object of the same or another class).
• Member methods: They are the operations applicable to an object of the class. They can modify all or part of an object’s state and return calculated values based on that state.

Inheritance:

Inheritance (class derivation): the mechanism that allows creating a class (derived class, subclass, or child class) from an existing class (superclass or parent class).

Inheritance ≡ (Generalization/Specialization relationship between classes)

• Inheritance is like passing down family traits from one generation to the next. Children inherit characteristics, skills, and sometimes even responsibilities from their parents.

Types of Inheritance

• Single Inheritance: a class can inherit only one superclass.

• Multiple Inheritance: some object-oriented languages, such as C++, allow for multiple inheritance, which means they offer the possibility of inheriting a class from two or more superclasses. This technique allows grouping attributes and methods of multiple classes into a single class.

• Example: Think of a family tree where the superclass represents common traits passed to all descendants.

Polymorphism:

It is the object’s ability to belong to multiple classes:

POLYMORPHISM ≡ (OBJECT’S ABILITY TO HAVE MULTIPLE FORMS)

• Polymorphism is like a universal remote control. It doesn’t matter what brand or model your TV is; the remote can control them all. In programming, polymorphism allows you to interact with different objects in a consistent way, regardless of their specific types.

Types of Polymorphism

• Ad-hoc polymorphism (overloading)
• Parametric polymorphism (generics)
• Inheritance polymorphism (overriding)

Encapsulation:

It is a mechanism (also called abstraction) that involves grouping data and methods within a structure while hiding the object’s implementation.

ENCAPSULATION ≡ DATA PROTECTION (public or private)

• Encapsulation is like a car’s dashboard. When you drive a car, you don’t need to know how the engine works; you interact with the dashboard, which provides access to essential controls while hiding the complex machinery underneath.

• Encapsulation allows defining visibility levels for class elements to provide access rights to data via a method of the class itself, a subclass, or any class.

Visibility Levels

• Public: functions from all classes can access the data or methods of a class defined with public visibility.

• Protected: only member functions of the subclass and its descendants can access the data.

• Private: only methods of the class itself can access the data.

• These visibility levels are like different levels of access to the dashboard controls: public (anyone can use them), protected (only authorized users), and private (only the driver).