Object-Oriented Programming

• Lets assume we want to learn car driving
  • Know everything: Understand how car engine works, ac works
  • Or will you try to operate car using the abstractions like steering, dashboard, clutch, accelarator etc
  • Steering hides the complexity of rotating tyres and gives you simple abstracted interface
• When we humans learn to use objects we use the abstracted interfaces.
• When we try to design program’s/applications why don’t we follow this approach?
• This thought process has led to object-oriented programming
• Generally anything or everything is an object.
• Every object will have contents (What it has or what it is made of) and characteristics (What it can do)
• Lets take television as an example

contents: 
   screen
   hdmi ports
   usb ports
   motherboard
characteristics:
   playmovies
   connect to satellite channels

• Lets take car as an example

contents:
    engine
    wheels
    dashboard
characteristics:
    start_the_engine
    commute
    stop_the_engine

• Lets take bank account as an example

contents:
    account holders name
    account id
    address
    balance
characteristics:
    deposit_amount
    withdraw_amount
    transfer_amount
    pay_bills

• When we work on object-oriented programming we call contents as members and characteristics as methods.
• Members represent data and methods represent behaviors.
• Generally when we think of system we will have multiple objects.
• The following are major relations
  • Inheritance:
    • What does it mean Captian America is a soldier or Stark is an engineer or car is a vehicle
    • In this relation we have two objects parent object (soldier/engineer/Vehicle) and child objects (Captian America, Stark, car) which have same contents or capabilities/behaviors as a parent
    • Inheritance in simple is a relation that can be expressed as is a relationship
  • Composition:
    • What does it mean by Bus has a driver or wall has a clock or laptop has a webcam
    • In one object other object is composed/present
    • When any relationship b/w two objects can be expressed as has a it is Composition
• The design time entity of object is called as class. we use class to create multiple objects.

Terms

• Object Oriented Analysis (OOA):
  • We will look into real world problem and analyze the problem and write requirements with objects into consideration
• Object Oriented Design (OOD):
  • From the requirements we create a design (UML) with objects and their relationships
• Object-Oriented Programming (OOPS):
  • Implementation of the design created by OOD in some object-oriented language like C#, Java, Python etc…