![Object-Oriented Programming (OOP) and Its Principles Object-Oriented Programming (OOP) is a programming paradigm based on the concept of objects, which can contain data, in the form of fields (often known as attributes or properties), and code, in the form of procedures (often known as methods). OOP aims to incorporate the principles of real-world objects into programming, allowing for a more intuitive way to handle complex software projects. The core principles of OOP are Encapsulation This principle is about bundling the data (attributes) and methods that operate on the data into a single unit called an object. It also involves restricting access to the inner workings of that object (data hiding), which can prevent accidental modification of data. Inheritance This allows a class to inherit properties and methods from another class. The class that inherits is called the child or subclass, and the class being inherited from is called the parent or superclass. Inheritance promotes code reusability and can make code more organized and manageable. Polymorphism This principle allows objects of different classes to be treated as objects of a common superclass. It is the ability for the same code to be used with different types of objects to produce different outcomes. Polymorphism can be achieved through method overriding (where a child class has a different implementation of a method already defined in its parent class) or method overloading (where two methods have the same name but different parameters). Abstraction This principle involves hiding complex implementation details and showing only the necessary features of an object. It can reduce programming complexity and increase efficiency. Sample Python Code Demonstrating OOP Principles Let's create a simple Python example to demonstrate these principles # Base class Animal (demonstrates Abstraction) class Animal def __init__(self, name) self.name = name # Encapsulation - name is a property of the animal def speak(self) # Abstraction - Specific animals will implement this raise NotImplementedError(Subclass must implement abstract method) # Child class Dog inheriting from Animal (demonstrates Inheritance) class Dog(Animal) def speak(self) # Polymorphism - Overriding the speak method return f{self.name} says Woof! # Child class Cat inheriting from Animal class Cat(Animal) def speak(self) # Polymorphism - Overriding the speak method return f{self.name} says Meow! # Creating objects dog = Dog(Buddy) cat = Cat(Whiskers) # Demonstrating polymorphism animals = [dog, cat] for animal in animals print(animal.speak()) # Even though they're different, we can treat them as the same type of object (Animal). In this example Encapsulation is demonstrated by encapsulating the name attribute in the Animal class. Inheritance is shown where Dog and Cat classes inherit from the Animal class. Polymorphism is shown in how both Dog and Cat classes can use the speak method, but implement it differently. Abstraction is shown by defining a method speak in the Animal class, which is then implemented by its subclasses. The Animal class cannot be instantiated on its own because it contains a method speak that is not implemented, making it abstract in nature. This code provides a simple yet comprehensive demonstration of the key OOP principles, making it a good starting point for learners.](https://miltonmarketing.com/wp-content/uploads/2018/04/Object-Oriented-Programming-.webp "Object-Oriented Programming (OOP) 6")
Object-Oriented Programming (OOP) is a programming language paradigm based on the concept of “objects“, which may contain data, in the form of fields, often known as attributes; and code, in the form of procedures, often known as methods.
A feature of objects is that an object’s procedures can access and often modify the data fields of the object with which they are associated (objects have a notion of “this” or “self“). In OOP, developers design computer programs by creating objects that interact with one another.
OOP languages vary significantly, but most popular ones use a class-based approach. In these languages, classes define objects and typically determine their type.
Many of the most widely used programming languages (such as C++, Object Pascal, Java, Python etc.) are multi-paradigm programming languages that support object-oriented programming to a greater or lesser degree, typically in combination with imperative, procedural programming.
Significant object-oriented languages include Java, C++, C#, Python, PHP, Ruby, Perl, Object Pascal, Objective-C, Dart, Swift, Scala, Common Lisp, and Smalltalk.
The Basic OOP Concepts
If you are new to object-oriented programming languages, you will need to know a few basics before you can get started with code. The following definitions will help you better understand object-oriented programming:
- Abstraction: The process of picking out (abstracting) common features of objects and procedures.
- Class: A category of objects. The class defines all the common properties of the different objects that belong to it.
- Encapsulation: The process of combining elements to create a new entity. A procedure is a type of encapsulation because it combines a series of computer instructions.
- Information hiding: The process of hiding details of an object or function. Information hiding is a powerful programming technique because it reduces complexity.
- Inheritance: a feature that represents the “is a” relationship between different classes.
Interface: the languages and codes that the applications use to communicate with each other and with the hardware. - Messaging: Message passing is a form of communication used in parallel programming and object-oriented programming.
- Object: a self-contained entity that consists of both data and procedures to manipulate the data.
- Polymorphism: A programming language’s ability to process objects differently depending on their data type or class.
- Procedure: a section of a program that performs a specific task.
Objects and classes
Languages that support object-oriented programming typically use inheritance for code reuse and extensibility in the form of either classes or prototypes. Those that use classes support two main concepts:
Classes – the definitions for the data format and available procedures for a given type or class of object; may also contain data and procedures (known as class methods) themselves, i.e. classes contain the data members and member functions
Objects: Instances of Classes
Real-World and Abstract Representations
Objects sometimes correspond to real-world entities. For example:
- A graphics program might have objects such as “circle,” “square,” and “menu.”
- An online shopping system could include objects like “shopping cart,” “customer,” and “product.”
Objects can also represent abstract entities, such as:
- An object that represents an open file.
- An object that translates measurements between U.S. customary and metric systems.
Objects and Classes
Each object is an instance of a specific class. For example, an object with its name field set to "Mary" could be an instance of the Employee class.
In object-oriented programming (OOP):
- Procedures are referred to as methods.
- Variables are also known as fields, members, attributes, or properties.
This leads to the following distinctions:
- Class Variables: Belong to the class as a whole, with only one copy shared among all instances.
- Instance Variables or Attributes: Contain data unique to each object, with every object maintaining its own copy.
- Member Variables: A general term referring to both class and instance variables defined by a class.
- Class Methods: Belong to the class as a whole and can only access class variables and procedure inputs.
- Instance Methods: Belong to specific objects and can access instance variables, class variables, and inputs.
Object Behavior and Access
Objects behave like variables with a complex internal structure. In many programming languages, objects are effectively pointers, serving as references to specific instances in memory. These references typically reside in the heap or stack.
Objects provide a layer of abstraction, separating internal functionality from external access. External code can:
- Call a specific instance method with input parameters.
- Read an instance variable.
- Write to an instance variable.
Creating and Managing Objects
Objects are created using a constructor, a special method in the class. A program may create many instances of the same class during runtime. These instances operate independently, allowing the same procedures to be applied to different sets of data.
Class-Based vs. Prototype-Based Programming
Object-oriented programming that uses classes is referred to as class-based programming. In contrast, prototype-based programming does not typically use classes. Instead, it relies on significantly different yet analogous terminology to define objects and instances.
Additional Composition Features
In some languages, classes and objects can incorporate concepts like traits and mixins to extend functionality and enhance code reuse.
Object-Oriented Programming (OOP) – Class definition, and instances.
Class-based vs prototype-based
In class-based languages, the classes are defined beforehand and the objects are instantiated based on the classes. If two objects apple and orange are instantiated from the class Fruit, they are inherently fruits and it is guaranteed that you may handle them in the same way; e.g. a programmer can expect the existence of the same attributes such as colour or sugar content or is ripe.
In prototype-based languages, the objects are the primary entities. No classes even exist. The prototype of an object is just another object to which the object is linked. Every object has one prototype link (and only one). New objects can be created based on already existing objects chosen as their prototype.
You may call two different objects apple and orange a fruit if the object fruit exists, and both apple and orange have fruit as their prototype. The idea of the fruit class doesn’t exist explicitly, but as the equivalence class of the objects sharing the same prototype. The attributes and methods of the prototype are delegated to all the objects of the equivalence class defined by this prototype. The attributes and methods owned individually by the object may not be shared by other objects of the same equivalence class; e.g. the attributes sugar content may be unexpectedly not present in apple. Only single inheritance can be implemented through the prototype.
Lets create some code. Lets talk some OOP (Object Oriented Programming.) I’m gonna drop my new album on you… :-)
You down wit OOP ?
You down wit OOP ? yeah you know me
Fun Aside: Back to the Keyboard
After you finish with your clock chain necklace and booty bouncing, let’s get back to the keyboard. Enough fun and games.
Game Development Example: A Hypothetical GTA-Style Game
The Role of Car Classes
Hypothetically, let’s say we are making a video game similar to GTA (Grand Theft Auto). In game development, having multiple car classes adds variety and complexity. For instance, cars like the Progen Emerus and Declasse Scramjet can represent distinct vehicle classes.
Designing a system with 50 or more potential car classes may seem complex, especially when creating numerous instances of each class.
Scaling Complexity: Cars and Citizens
Imagine a large urban environment, such as Los Angeles, with a population of approximately 3.8 million people. Each citizen could potentially own one or more cars from the 50 available classes.
If every citizen owns one car from each class, the total number of cars in the game world would be staggering, demonstrating the need for efficient class and instance management.
Understanding Classes in Object-Oriented Programming
The Purpose of a Class
A class organizes information about a type of data, enabling programmers to reuse elements when creating multiple instances of that data type. For example, if a programmer wanted to create three car instances—a BMW, a Ferrari, and a Ford—they could use a single Car class.
The Car class allows the programmer to store shared information (like color, model, and make) while associating unique attributes with each instance.
Classes as Blueprints for Objects
In object-oriented programming, a class serves as a blueprint for creating objects (a specific data structure). It defines:
- Initial values for state (member variables or attributes).
- Behavior implementations (member functions or methods).
Using the class keyword, developers define classes to manage objects. An instance is a specific object created from a class. For example, an individual car, such as a red BMW, represents an instance of the Car class.
Key Features of Classes
Code Reusability Through Inheritance
Classes not only manage objects but also support inheritance, which allows programmers to reuse code. Inheritance is a key component of object-oriented programming, enabling efficient management of related objects while reducing redundancy.
The image above shows how a Car object can be the template for many other Car instances. In the image, there are three instances: polo, mini, and beetle.
Here, we will make a new class called Car, that will structure a Car object to contain information about the car’s model, the color, how many passengers it can hold, its speed, etc. A class can define types of operations, or methods, that can be performed on a Car object.
For example, the Car class might specify an accelerate method, which would update the speed attribute of the car object.
For example, the Car class might specify an accelerate method, which would update the speed attribute of the car object.
Object-Oriented Programming (OOP) and Its Principles
Object-Oriented Programming (OOP) is a programming paradigm based on the concept of “objects”, which can contain data, in the form of fields (often known as attributes or properties), and code, in the form of procedures (often known as methods). OOP aims to incorporate the principles of real-world objects into programming, allowing for a more intuitive way to handle complex software projects. The core principles of OOP are:
- Polymorphism: This principle enables treating objects of different classes as if they belong to a common superclass. Developers use polymorphism to write the same code for different types of objects, allowing it to produce varying outcomes. Method overriding achieves polymorphism by letting a child class implement a method differently from its parent class. Method overloading offers another approach, where two methods share the same name but differ in their parameters.
- Abstraction: This principle involves hiding complex implementation details and showing only the necessary features of an object. It can reduce programming complexity and increase efficiency.
- Encapsulation: This principle is about bundling the data (attributes) and methods that operate on the data into a single unit called an object. It also involves restricting access to the inner workings of that object (data hiding), which can prevent accidental modification of data.
- Inheritance: This allows a class to inherit properties and methods from another class. A child or subclass inherits from a parent or superclass. Inheritance promotes code reusability and can make code more organized and manageable.
Sample Python Code Demonstrating OOP Principles
Let’s create a simple Python example to demonstrate these principles:
In this example:
- Encapsulation: is demonstrated by encapsulating the
nameattribute in theAnimalclass. - Inheritance: is shown where the
DogandCatclasses inherit from theAnimalclass. - Polymorphism: is shown in how both
DogandCatclasses can use thespeakmethod but implement it differently. - Abstraction: is shown by defining a method
speakin theAnimalclass, which is then implemented by its subclasses. TheAnimalclass cannot be instantiated on its own because it contains aspeakmethod that is not implemented, making it abstract in nature.
This code provides a simple yet comprehensive demonstration of the key OOP principles, making it a good starting point for learners.
Here’s how the OOP concepts would look in a code-like format without using any special formatting:
1. Encapsulation
Class Car:
Property speed
Method accelerate():
Increase speed by 2
Once a Car is created:
Set speed to 0
Create a Car object
bmw = Car()
bmw.accelerate()
2. Abstraction
Class Car:
Hide internal details of accelerate()
Method drive():
Call accelerate() and handle other actions
Create a Car object
bmw = Car()
bmw.drive()
3. Inheritance
Class Car:
Property speed
Method accelerate()
Class ElectricCar inherits from Car:
Property battery_level
Create an ElectricCar object
tesla = ElectricCar()
tesla.accelerate()
4. Polymorphism
Class Car:
Method horn():
Print “Regular car horn sound”
Class Truck inherits from Car:
Override horn():
Print “Loud truck horn sound”
Create a Car object and a Truck object
bmw = Car()
truck = Truck()
bmw.horn() # Prints “Regular car horn sound”
truck.horn() # Prints “Loud truck horn sound”
Full Example (Combining All Concepts)
Class Vehicle:
Method start():
Print “Vehicle is starting”
Class Car inherits from Vehicle:
Property speed
Property color
Method accelerate()
Class Motorcycle inherits from Vehicle:
Override start():
Print “Motorcycle is roaring to life”
Create Car and Motorcycle objects
bmw = Car()
motorcycle = Motorcycle()
bmw.start() # Prints “Vehicle is starting”
motorcycle.start() # Prints “Motorcycle is roaring to life”
To demonstrate Object-Oriented Programming (OOP) concepts effectively, I’ll write a complete Python example that implements these ideas clearly. Here’s how these concepts can be realized:
Full Python Code Example
Key Features:
- Encapsulation: The
__speedattribute in theCarclass is private and accessed using public methods. - Abstraction: The
AdvancedCarclass hides the details of how the car accelerates and combines actions in thedrivemethod. - Inheritance: The
ElectricCarclass inherits fromCarand adds additional functionality with acharge_batterymethod. - Polymorphism: The
startmethod behaves differently forMotorcycleandVehicle. Thehornmethod inTruckoverrides behavior inCar.
