OOP Lesson 1

Object-Oriented Programming

Lesson 1: Introduction to OOP

​What is Object-Oriented Programming?

​OOP in Action

• The OOP paradigm is focussed on objects​ which represent parts of a computer program.

• ​You can create objects to represent physical things, like a human being.

• ​They can also be used for small parts of a larger program, like a widget in a user interface.

​Classes

• To create objects, you must first define a class.​

• ​A class is like a blueprint, it contains the plans for the data and behaviours an object should possess.

• ​You can create many objects from a single class.

• ​Just like you can make many houses from the same blueprint.

​Objects

• You can use a class to create enemies in a video game.

• ​One class details what information the enemies can hold and the behaviour it has.

• ​Objects would be the actual enemies in the game.

• ​Each ghost is an object in the game with a slightly different behaviour.

PACMAN with Turtle - Replit

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​Object Behaviour

• Ghost objects can choose their own behaviour based a the set of defined rules.

• ​Each ghost has its own attributes: colour, speed, name.

• ​They all move independently of each other.

​Classes and Objects

• ​One of the classes used in this program is called turtle.

• ​We import the class so that it can be used to make objects.

• ​The objects created are: blinky, pinky, inky and clyde.

• ​These are actually the variables used to store the objects.

Multiple Choice

A template used to create objects...

• Subroutine

• Function

• Class

Multiple Choice

An instance of a class...

• Object

• Function

• Variable

​Introduction to C#

​C#

This programming language can be used to make interactive websites, mobile apps, video games, augmented reality (AR), virtual reality (VR), desktop applications, and back-end services – just to name a few.

For example, the mobile game Pokemon Go and the Stack Overflow website were built with frameworks that can be run with C# (Unity and ASP.NET, respectively).

• Unlike languages like Ruby and JavaScript, C# has you define the type of each data in a program.

• ​Assigning a type essentially tells a computer what operations can and cannot be performed on a piece of data.

• ​This style of coding helps programmers avoid a large class of errors that are common to Ruby and JavaScript.

​C# Data Types

​Hello World

​Console.WriteLine() is a command that prints text to a console.

​

Whatever is in between the parentheses will be printed to the console!

​

In this case it’s Hello World!

​Task: Start a new project in Visual Studio and change the code so that your own name is printed to the console!

HelloWorld - Replit

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​Getting Input

​We can also read input from a user. The command Console.ReadLine() captures text that a user types into the console.

​

In this example, the program writes a question to the console and waits for user input. Once the user types something and presses Enter (or Return), the input is printed back out to the user.

​Comments

Text written in a program but not run by the computer is called a comment.

​

In C#, anything after a // or between /* and */ is a comment.

Comments can:

​Provide context for why something is written the way it is:

​Help other people reading the code understand it faster:

​Ignore a line of code and see how a program will run without it:

Multiple Choice

In C#, what are these lines of code called?

• Output

• Comments

• Inputs

• Commands

Multiple Choice

What is the outcome of these lines of code?

• The text "Let's get started" is printed

• No text is printed until the user types into the console

• The text "Press Enter to begin..." and the computer waits for the user to press Enter

• The texts "Press Enter to begin..." and "Let's get started!" are printed

Multiple Choice

What is the outcome of this line of code?

• The computer waits for the user to type something

• The computer outputs whatever the user last entered

• The computer outputs "Console.ReadLine()"

• The computer copies all of the text in the console

Multiple Choice

What is the outcome of this line of code?

• The text WriteLine is printed

• The text Console.WriteLine("Open Sesame!") is printed

• The text "Open Sesame" is printed

• No text is printed

Multiple Choice

What is NOT a good reason to use comments in your code?

• Ignore a line of code to see how a program will run without it

• Provide context why something is written the way it is

• Help other people reading the code to understand it faster

• To instruct a computer to execute a block of code

ConsoleCreatures - Replit

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