If you missed part 1, i suggest to take a look. It has some good information in it to understand what programming is really all about.
 

Introduction

Programming is all about information flow. To make information flow in programming we have the following tools to our disposal:

1. Events
2. Methods
3. Properties

1. Events

Events are signals that something has happened. Events execute an empty piece of code automatically, which programmers can fill with anything that needs to happen. Common examples of events are: "a key on the keyboard has been pressed" or "a button has been clicked".

2. Methods

Methods are collections of code that belong together that can be executed at any time you want. Common examples of methods are: "update data on screen" or "initialization".

3. Properties

Properties are pieces of information that are saved in the memory of the computer. Common examples of properties are: "color" or "size".
 

Object-ortiented programming

Object-oriented programming (OOP) is a very structured way of programming to make it clearer for humans to write code. As the name suggests, it works with objects. An object is a structured collection of information and can be put into the memory of a computer by executing code from something named a class so it can be used by anything that has access to the memory. This process is called "instancing" (creating an instance of an object).

Classes

A class is a blueprint of an object. A class describes all events, methods and properties that the object will gain when it's instanced. The beautiful thing about this blueprint is that you can also use this blueprint in other blueprints! An example of this is a "vehicle". Cars and bicycles are both vehicles , but have distinct differences.
 

Practical example

Let's look at how much easier programming is when using OOP. We are going to use the car and bicycle in the following example project:

The user has to pick a vehicle. After picking the vehicle the user can:

1. See properties of the chosen vehicle (we'll keep it simple with just the weight and color)
2. Execute a warning sound based on what vehicle was chosen (horn for the car and bell for the bicycle)

Implementation 1 (no OOP):

Main application

Events:

• User has chosen a vehicle (VehicleChosen with the property ChosenVehicle as parameter)
• User wants to see properties of the chosen vehicle (VehiclePropertiesRequest)
• User wants to execute a warning sound (WarningSoundRequest)

Methods:

• Execute code at the start of the application (Initialize)
• Show bicycle properties (ShowBicycleProperties)
• Show car properties (ShowCarProperties)
• Ring the bell of the bicycle (RingBell)
• Hunk the horn of the car (HunkHorn)

Properties:

• ChosenVehicle (number)
• Car weight (number)
• Car color (color)
• Bicycle weight (number)
• Bicycle color (color)
   

VehicleChosen

• If bicycle is chosen set ChosenVehicle to 1
• If car is chosen set ChosenVehicle to 2

VehiclePropertiesRequest

• If the user has chosen the bicycle: ShowBicycleProperties
• If the user has chosen the car: ShowCarProperties

WarningSoundRequest

• If the user has chosen the bicycle: RingBell
• If the user has chosen the bicycle: HunkHorn

Initialize

• Load the vehicle data

ShowBicycleProperties

• Show bicycle weight and car color

ShowCarProperties

• Show car weight and car color

RingBell

• Ring the bell

HunkHorn

• Hunk the horn

 

Implementation 2 (OOP):

Blueprint for vehicle

Methods:

• Execute code at the start of the application (Initialize)
• WarningSound

Properties:

• Weight (number)
• Color (color)

Blueprint for bicycle

Inherit everything from the vehicle blueprint.

WarningSound

• Ring the bell

Blueprint for car

Inherit everything from the vehicle blueprint.

WarningSound

• Hunk the horn
   

Main application

Events:

• User has chosen a vehicle (VehicleChosen with the property ChosenVehicle as parameter)
• User wants to see properties of the chosen vehicle (VehiclePropertiesRequest)
• User wants to execute a warning sound (WarningSoundRequest)

Properties:

• ChosenVehicle (vehicle)
   

VehicleChosen

• If bicycle is chosen set ChosenVehicle to bicycle
• If car is chosen set ChosenVehicle to car

VehiclePropertiesRequest

• Show ChosenVehicle.weight and ChosenVehicle.color

Initialize

• Load the vehicle data

WarningSoundRequest

• Execute ChosenVehicle.WarningSound
   

Closing arguments

You can see how much more logical and clear it is with OOP and this is a relatively simple application. Imagine having to write software with 100's of objects without OOP, it's going to make your head explode really quickly! I hope you start to see how awesome programming is if you know what you're doing. So if you like a challenge and a good salary, programming might be just the thing for you :)

See you in the next lesson!