Object Oriented Programming (OOP) Introduction

Introduction to
OOP Concepts
BY: SAMUEL ANSONG

Pre-Requisites
• Familiarity with functions and types
• Basic understanding of a class
• Has an overall Introduction to programming
• We will be using C# for code samples

Pre-Requisite Check
1. Write a simple function to add all numbers in the array below
int [] array = new int[] {2,4,5,6,7,8,8,9,0,10,5,7}
Hint
<visibility> <return type> <name>(<parameters>)
{
<function code>
}
You can logon Here -> C# Online Compiler | .NET Fiddle (dotnetfiddle.net) and complete your
code.

Answer and Modification
1. Overload the function to take 3 numbers
2. Overload the method to take any amount of numbers
3. Change the function into a lambda format

Structure
Procedural Oriented Programming Overview
Limitations of POP
Object Oriented Programming Overview
• Encapsulation
• Inheritance
• Polymorphism
• Abstraction
Core Components
• Access Modifiers
• Static Class and Methods
Key Terms

Procedural Oriented Programming
• C , Pascal, FORTRAN, and similar languages are procedural languages
• Each Statement in the language tells the computer to do something
• Get some Input
• Add these numbers
• Divide by 4
• Display the number
A program in a procedural language is a list of
instructions

Divided Into Functions
• Procedural program is divided into functions
• Each function has clearly defined purpose and how it interfaces with other
functions in the program
• One can also further extend functions by grouping several functions together
into a larger entity called Modules .

Divided Into Functions
• In Multi-Function program important data items
are placed as Global so that they maybe
accessed by all functions
• Each function may also have its own local data

Limitations for POP
• Since all functions have accessed to the Global Variable , new functions
accidentally created can corrupt the data
• We can access the data of one function from other since there is no
protection
• In a large program it is difficult to trace what data is used by which function
• If new data is added , all the functions are to be modified to access this data

Object Oriented Programming
• OOP was introduced to overcome flaws in the procedural
approach to programming
• Such as lack of Reusability and Maintainability
• The Fundamental idea behind OOP is to combine into a
single unit both data and functions that operate on them.
• Such a unit is called an Object .

Objects?
In the real world, just about anything can be seen as an object:
car, dog, person, department, city, etc. These
have state and behavior. For example, a dog's state is its color,
breed and name; its behavior is the way it barks, runs or wags its
tail. Objects in OOP are quite similar

Example
Identify the Properties (State) and Behavior
(Methods) of Your Bicycle

Object Oriented Programming
• In OOP, problem is divided into number of entities called objects
and then builds data and functions around these objects
• It ties the data more closely to the functions that operate it and
protects it from accidental modification from the outside functions
• Data of an object can only be accessed by the functions associated
with that object
• Communication of the objects done through functions.

Classes
• Classes are user-defined data types
• Objects are variables of a class
• Once a class has been defined, we can create any number of
objects from the Class
• A class thus can be said as a collection of similar objects of same
type.

Example
• Let us consider a software that involves renting cars.
• We can have a class and objects as below

Example
Let us consider a software that involves a zoo.
What are some of the classes and objects to be
created .

Encapsulation
• Encapsulation is the first pillar or principle of object-oriented
programming
• In simple words, “Encapsulation is a process of binding data
members (variables, properties) and member
functions(methods) into a single unit”
• And a Class is the best example of encapsulation
• Data Hiding from all external Classes

Encapsulation in Real Life
•Has prescription
•Does not have direct
contact to the medicines
Patient
•Has Access to the medicine
•Returns the right medicine
•Reduces risk of you getting
wrong medicine
Chemist •Can only be accessed by
chemists
•Several medicines available
for different treatments
Medicines

Encapsulation in OOP
•Has no direct access to
data in the medicine class
External
Classes
•Controls access and
manipulation of data in the
medicine class
•They are wrapped in the
class
Functions •Medicine Class
•Contains both member
functions and Variables
•Determines how accessible
the data is to outside world
Medicines

Encapsulation in OOP
So, Encapsulation means hiding the important features
of a class which has no usefulness being
exposed to outside of the class and exposing only the
necessary things of the class.

Abstraction
Abstraction is about describing something at a
conceptual level while leaving out the details.
example, we may talk about a vehicle without
being explicit if it's a ship or a car.

Example of Abstraction
When using the tv remote control, you do not
bother about how pressing a key in the remote
changes the channel on the TV. You Just know
that pressing the “+” volume button will increase
the volume.

• A class can be abstract as well meaning , it can provide you
functions without their implementation
• For example, if our class was a remote control , it will give
us the method IncreaseVolume() without details of how It
will be done . Such a method is called an abstract method

• You cannot instantiate this class
Animal myObj = new Animal(); // Will generate an
error
• You can only Inherit this class

Inheritance
• The mechanism of deriving a new class from an old class is called
inheritance or derivation
• The Old class is known as base class while new class is known as
derived class or sub class
• Inheritance is the most powerful feature of OOP.
• Gives the sub class access to methods of based class

Example
If a child is as Tall as his dad and Fair as his mom
, we usually say the child has inherited these
features from his father and mother.

Example
using System;
namespace MyApplication
{
class Vehicle // Base class
{
public string brand = "Ford"; // Vehicle field
public void honk() // Vehicle method
{
Console.WriteLine("Tuut, tuut!");
}
}
}
• The Base class here is Vehicle
• It has Properties (Brand) and an implemented
Method honk

Example
using System;
{
class Car : Vehicle // Derived class
{
public string modelName = "Mustang"; // Car field
}
}
• The Base class here is Vehicle
• The Car class is inheriting the vehicle class and thus
Will have access to the honk method in the Vehicle class.
• Inheritance is shown by the “:” sign . Colon.

Example Code Snippet
using System;
{
class Program
{
static void Main(string[] args)
{
// Create a myCar object
Car myCar = new Car();
// Call the honk() method (From the Vehicle class) on the myCar object
myCar.honk();
// Display the value of the brand field (from the Vehicle class) and the value of the modelName from the Car class
Console.WriteLine(myCar.brand + " " + myCar.modelName);
}
}
}

Inheritance
• Through Effective use of inheritance , you can save a lot of time in your
programming and reduces errors
• This will also increase the quality of the work and productivity

Polymorphism
• Polymorphism means "many forms", and it occurs
when we have many classes that are related to each
other by inheritance
• Inheritance lets us inherit fields and methods from
another class. Polymorphism uses those methods
to perform different tasks. This allows us to perform
a single action in different ways.

Example
For example, think of a base class called Animal that
has a method called animalSound(). Derived classes of
Animals could be Pigs, Cats, Dogs, Birds - And they
also have their own implementation of an animal
sound (the pig oinks, and the cat meows, etc.):

Example
class Animal // Base class (parent)
{
public void animalSound()
{
Console.WriteLine("The animal makes a sound");
}
}
class Pig : Animal // Derived class (child)
{
public void animalSound()
{
Console.WriteLine("The pig says: wee wee");
}
}

Next Lecture
Object Oriented Programming Implementation
Building a Game with C#
Unity 3D and C#
• Encapsulation
• Inheritance
• Polymorphism
• Abstraction
Modelling our Game as OOP

Object Oriented Programming (OOP) Introduction

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