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Designing a Component-
based Architecture in Lua
for Game Apps
半路 / Jheng Wei Ciao
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Pitfalls in
Object-Oriented Design
?!
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Traditional OOD
Object-Oriented Design
Class
Inheritance
Virtualization
Polymorphism
Inheritance-based Architecture
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Player Enemy
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Actor
Player Enemy
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Actor
WalkableObject
Player Enemy
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CollidableObject FlyableObject
Player Enemy
Actor
WalkableObject
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CollidableObject FlyableObject
FlyingEnemy
Actor
WalkableObject
How?
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CollidableObject FlyableObject
FlyingEnemy
FlyingActor
How?
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Pitfalls in IBA
Deep and tangled hierarchies
Diamond ring inheritance
Copy-paste code here and there
Special cases
“Warning: don’t touch this!”
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Component-based Architecture
Each functionality is a game component
Data-driven method for objects creation
Design Patterns: “Favor composition over
inheritance”
Game Engine: Unity 3D
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Player
WalkableObject
CollidableObject
FlyableObject
Enemy
WalkableObject
CollidableObject
FlyableObject
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WalkableObject
CollidableObject
FlyableObject
Game
Components
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WalkingEnemy
FlyingEnemy
WalkableObject
CollidableObject CollidableObject
FlyableObject
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Why Lua?
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Advantages in Lua
Lightweight, extensible, cross-platform
Robust
Freedom
Simply love it
Other programming languages?
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Drawbacks in Lua
Most editors don’t support auto-completion code
Goodbye to debuggers & breakpoints
Hello to loggers & print()
No excuse for coffee break time
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Don’t use CBA... yet
CBA can’t save the (your) world
OOD can do good things too
Don’t make everything a component
Leave messy code alone
You might need an editor or tool
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Pitfalls in Lua
Naming convention for global variables
Do garbage collection manually
Don’t forget to compile scripts & strip debug info
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My Lua Trilogy
Lua
5.1.5
Luabind
0.9.1
Time-saver & OO-like
Boost
Luabind depends: template programming
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My Programming Trilogy
C++
Generic framework
Objective-C
iOS platform-specific
OpenGL ES implementation
Lua
Data description
Game logic
10%
65%
25%
C++ Lua Objectitve-C
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Basic Architecture &
Components
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Player
Transform
BoundingBox
Quad
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Meet Powerful ‘Table’
Player = {}
Player[“Transform”]
Player[“Quad”]
Player[“Transform”]:SetTranslate(50, 100)
Player[“Quad”]:SetSize(120, 120)
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Traditional OOP
Game Objects Update
#1 #2 #3 #4 #5
Game Objects Render
#1 #2 #3 #4 #5
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Component-Based Architecture
Game Components Update
#1 #2 #3 #4 #5
Game Components Render
#1 #2 #3 #4 #5
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Game Object = Container
Game Object
Transform
Bounding
Sprite
Motion
StateMachine
Timer
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Object Factory
Game Component
Templates
Game Object
Templates
Game-based
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Interpolator GC
0 255
0.1 1.0
SetAlpha()
SetScale()
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Memory Management
Lua
Game Object
Transform
Sprite
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Memory Management
C++
Transform
Sprite
......
Lua
Game Object
Transform
Sprite
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User Interfaces & Widgets
Widgets
Button Picture
Text Number
Radio Button Progress Bar
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Widgets Functionalities
Widgets
Button
Render/Update
Movement
Scale Up/Down
Fade In/Out
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Widgets = Container
Widgets
Button
Sprite
Motion
Transform
Fade
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MainMenu
Button
Sprite
Interpolator
Input Events
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Live Demo
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[Launching Xcode]
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Live Game Apps?
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《Bonnie’s Brunch 2》
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《Jade Ninja》 Jan. 2013
Coming Soon
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If you are into Lua...
Step 1) Data description/serialization
Step 2) User interface
Step 3) Game logic
Warning: Don’t use Lua for everything
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Live Well,
Happy Coding,
Make Great Games!