Object-Oriented Programming (OOP)

• This chapter introduces Object-Oriented Programming (OOP)
• The theory provides knowledge necessary to use OOP with expertise.
• This OOP theory provides the basis for coding an actual Pong game project.
• The chapter covers OOP and classes using a hypothetical Bat class and start working on the Pong game and code a real class to represent the player's bat.

OOP Paradigm

• OOP is a programming paradigm considered to be the standard way to code
• There are non-OOP ways to code, including non-OOP game coding languages/libraries
• Starting from scratch, there isn't any reason not to use OOP

Benefits of OOP

• Enables easier code management, changes, and updates
• Facilitates quicker and more reliable code writing
• Allows easy utilization of other people's code like SFML

Core Concept of OOP

• OOP programming involves breaking down requirements into manageable chunks called objects
• Objects are self-contained and reusable by other programs
• Classes serve as blueprints for objects.

Class Implementation

• Implementing an object of a class creates an instance of the class
• Classes in games represent real-world things
• Classes can be written for a bat controlled by the player or a ball bounced around the screen
• The core principles of OOP are encapsulation, polymorphism, and inheritance

Encapsulation Defined

• Encapsulation keeps the internal workings of code safe from outside interference
• Achieved by controlling access to variables and functions
• Enables code updates and improvements without affecting programs that use it

Polymorphism Defined

• This allows writing code less dependent on the types being manipulated
• Results in clearer and more efficient code
• "Polymorphism" means that objects can take on different forms

Inheritance Defined

• This allows harnessing features and benefits of other people's classes
• Includes encapsulation and polymorphism
• It refines code for specific situations

Advantages of Using OOP

• Facilitates adding new features without disrupting existing ones
• Encapsulation minimizes consequences when changing a class

Code Reusability

• Code can be used from other's without needing to know how it works inside
• Complicated concepts like multiplayer and directional sound can be used

Class Variations

• Similar, different versions of a class can be created using inheritance
• Original functions can be used for a new object

Planning and Design

• Planning and design are vital to successful OOP and game development,
• Well-structured code matters more than just knowing C++, SFML, and OOP topics
• Structuring code is called design patterns
• Effective use of design patterns becomes more important as code gets complex
• Design patterns can be learned as the complexity of projects grows

Class Defined

• A class is a collection of code containing functions, variables, and loops
• Each new class is declared in its own .h file with the same name
• Functions of the class are defined in its own .cpp file
• A class can be used to create multiple objects, with the class being the blueprint

Class Code Example

• The class keyword declares a new class in curly braces, followed by a semicolon
• Variables are declared
• These are prefixed with m_ as a convention
• Variables declared as part of a class are called member variables
• Private variables are not directly accessible by users
• Good encapsulation makes variables private whenever possible

Variables

• The public section solves the problem of private variables needing to be accessed
• Provides public functions to work with objects of the specified type
• In summary, there is a bunch of inaccessible (private) variables that cannot be used from the main function

Class Functions

• Class functions are in a separate file with the same name as the class and the .cpp extension
• Include directives are used to include class and function declarations from the .h file
• The scope resolution operator :: is used because the functions connect to a class
• The function name is prefixed with the class name, as well as ::

Instances

• An instance of the Bat class can be created:
  • Bat bat;
• Public functions can be accessed
• This can be used for code for multiplayer functionality
• Each instance of Bat has its own set of variables

Create Project

• To create a project, follow this:
• Start Visual Studio and click Create New Project button. If the Timber project is open, select File | New project.
• In the window, choose Console app and click Next button. The Configure your new project window will display.
• In the Configure your new project window, type Pong in the Project name field.
• Visual Studio configures the Solution name field automatically.
• In the Location field, browse to the VS Projects folder, where all project files are stored.
• Select the project properties by selecting Project | Pong properties from the main menu.

Additional configurations

• In the Pong Property Pages window, select All Configurations from the Configuration drop-down
• Select C/C++ and General from the left-hand menu.
• Locate the Additional Include Directories edit box and type the drive letter where the SFML folder is located, followed by \SFML\include.
• Select Linker, then General.
• Find the Additional Library Directories edit box, and type the SFML folder, followed by \SFML\lib.

Final Steps

• Select Linker and Input.
• Copy and paste/type sfml-graphics-d.lib;sfml-window-d.lib;sfml-system-d.lib;sfml-network-d.lib;sfml-audio-d.lib; into the Additional Dependencies edit box. Position the cursor carefully at the start.
• Click OK and then Apply.
• Copy the SFML.dll files into the main project directory from the SFML\bin folder.
• Create a new folder called fonts in the VS Projects\Pong folder to house the Heads Up Display (HUD).
• Add the DS-DIGIT.ttf file into the VS Projects\Pong\fonts folder.

Bat Class Intro

• Classes can be simple like the preceding Bat class, or contain other objects from other classes
• When making games, several things are missing from the hypothetical Bat class, for example drawing the Bat so it needs a sprite, and sometimes a texture

Bat.h Code

• We need a way to control the rate of animation for all game objects
• The Header File (.h) must be created
• #pragma once prevents processing the file more than once, speeding compilation

File Contents

• Vector2f is called m_Position, which holds the horizontal and vertical position of the player's bat
• SFML RectangleShape makes the bat appear on the screen
• Boolean: track direction
• Float: pixels per second when moving left/right
• Bat function is the constructor, meaning its the same name as its class

Functions

• getPosition: returns FloatRect (four points of a rectangle)
• getShape: returns RectangleShape
• Other Functions: for Bat movements.
• moveLeft/Right: controls if, when, and which way the bat moves.
• update: Calculates how to move the bat each frame.
• Calls an update function to the Bat instance and passes in the change in time.
• The Bat class gets the change in time and moves the bat based on the directions, the player moves them, and the desired speed of the bat.

Functions

• Classes: contains source code and is often split into a few parts, such as the member variable and function declarations
• Code: will detect if the player holds down the left arrow key; if so, the moveLeft will be called
• Main: handles the player quitting the game by pressing the Escape key
• Update: Bat object in our main game loop, or our draw function to call the getShape function
• Draw: Uses the rectangle shape from our current Bat object to draw to the screen

Summary of process

• New file created and saved as Bat.cpp
• Added constructors to Bat method
• In order to get the graphics, you use SFML libraries.
• When determining that positions are called we will get the positions of the graphics in the main loop