Object-oriented programming (OOP) is an essential skill in today’s programming job market. But if you’re only starting to program, don’t get intimidated by it.

The OOP concept is easy to grasp, especially if you’ve been into functional programming. OOP helps you write clean, scalable, and testable code.

But what is object-oriented programming, how does it work, and why do you need it?

What Is Object-Oriented Programming?

Question symbols

Object-oriented programming (OOP) is a coding design that uses data to represent a set of instructions. The OOP design revolves around dedicated classes you can instantiate as objects.

Unlike procedural or functional programming, OOP gives you the leeway to express code more comprehensively. While the former paradigms are often without structure, OOP encourages the use of dedicated structures called classes.

Methods are functions performing a specific task in the class. Attributes are like variables describing the class characteristics or features. Methods can run independently or often based on class attributes. Ultimately, both work together to actualize the OOP concept.

Advantages of Object-Oriented Programming

So how does object-oriented programming help you write a better program?

  • OOP reduces the complexity of your code base.
  • It helps you express your code clearly, making it more readable to others.
  • Programs written in OOP are typically more scalable.
  • It eases code testing and debugging.
  • OOP eliminates code duplication, establishing the DRY (do not repeat yourself) principle.
  • OOP code is often more modular, encouraging the separation of concerns.
  • Class composition and inheritance make your code more reusable.
  • Abstraction improves code-base security.

Drawbacks of Object-Oriented Programming

While the advantages of OOP outweigh its cons, the latter are still worth discussing:

  • It can be slower than functional programming.
  • OOP has a steep learning curve.
  • Script folders and files increase as the application scales.

The Object-Oriented Programming Structure

Arranged boxes in two different colors

OOP revolves around a strict architecture. Here are some of the terms you’ll come to know:

Class

A class is a collection of code presented as data performing similar actions. You can view a class as an object handler since you use one to instantiate objects.

Methods

Methods define how a class achieves its tasks. A class can contain one or more methods. You can view methods as ways a class shares responsibilities within itself.

For instance, a unit converter class might contain a method for converting Celsius to Fahrenheit. And it might include another method for changing grams to ounces.

Attributes

Attributes are the features—or properties—that describe a class. A unit converter class might contain attributes like the units of conversion, for instance. You can define methods that act on these attributes.

Like methods, you can access (some) attributes from a class instance.

Objects

Simply put, an object is the instance of a class. When you instantiate a class, the resulting object will use the class as a blueprint for its attributes and methods.

The Principles of Object-Oriented Programming

Object-oriented programming brings some principles to the programming table. Each of these gives it a lead over conventional programming.

Abstraction

The abstraction concept of OOP holds that you don’t need to know how something works to use it. It lets you wrap your code in simple words without bothering about the complexities behind the scene.

For instance, you don’t need to worry about the logic, filtering algorithm, or functions behind a submit action. All you see and care about as a user is the send button.

Object-oriented programming helps you abstract your logic by presenting individual tasks as single calls. For instance, while a unit converter class might calculate a lot behind the scenes, you could run its kilogram-to-gram converter by calling a single method: 

        class_instance.convert_gram()

Where class_instance is your object, and convert_gram is a method of the converter class.

Encapsulation

Encapsulation is one of the ways that object-oriented programming creates abstraction. Each object is a collection of data treated as an entity. The data within an object includes attributes and methods hidden from the global space.

Generally, encapsulation allows you to wrap your class data privately in an object. Thus, the content of one object doesn’t interfere with the other. And only an object’s inherent methods and attributes can alter it.

For instance, methods from a unit converter object shouldn't change the attributes of another object without inheritance or composition.

Encapsulation allows you to change an object’s content or structure without worrying about the public interface.

Inheritance

Inheritance allows you to reuse the content of a class, called a superclass, in another, called a child or subclass. When a class inherits a superclass, it automatically gains its attributes and methods.

In addition to the properties it inherits from the superclass, a subclass can also have its own attributes and methods.

Inheritance comes in handy if you want your class to use the data in an external module, for instance. It also ensures that you don’t repeat yourself while writing code.

So creating sub-classes also saves a lot of time. Instead of creating new classes for everything, you can create a base class and extend it to new sub-classes, borrowing the existing functionality.

Inheritance is useful, but knowing when to use composition instead is a fundamental programming principle.

Polymorphism

Polymorphism is a result of inheritance. It lets you maintain a method or attribute name in different objects where you can use them as you like.

This concept ensures that you can dynamically use a class method in different classes inheriting it from a base class.

For instance, a generic game object might define a movement method. Subclasses can define exactly how their specific movement occurs. Controlling code does not then need to know about how separate classes move, just that they all can move via a common method.

OOP vs. Functional Programming

OOP is popular, but programmers still use many other programming paradigms, depending on their needs. Functional programming is quite different from OOP:

  • Functional programming handles instructions in dedicated functions. OOP, on the other hand, presents instructions as data stored in objects.
  • In true functional programming, the output of a function is always the same and immutable. OOP allows polymorphism, and the returned data is mutable in other classes.
  • OOP is more scalable since you can easily extend objects.
  • Abstraction makes OOP more secure since an outsider doesn’t know the actions behind the scene. Functional programming can expose some layers.
  • Although OOP can be complex, it’s more maintainable than functional programming. Functional programming still retains some procedural attributes.
  • Functional programming can be faster since programs access instructions without considering object hierarchy. The object hierarchy is essential when working with object-oriented programs.

Time to Be Object-Oriented

The object-oriented programming concept can be hard to understand at first. But it becomes clearer once you start writing object-oriented code.

Remember that we've only discussed generalities in this article. While the OOP concept is similar across the board, each object-oriented language has its quirks and ways to make things happen. Once you choose the right language, you'll start to learn how it puts OOP principles into practice.