Using Lua to Build a Component-based Architecture for Game Apps

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Using Lua to Build a Component-based Architecture for Game Apps 半路 / Jheng Wei Ciao

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Component Based Architecture

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Lua

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Pitfalls of 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 WalkableObject Actor CollidableObject

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FlyableObject Player Enemy Actor WalkableObject CollidableObject

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CollidableObject FlyableObject FlyingEnemy Actor WalkableObject How?

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CollidableObject FlyableObject FlyingEnemy FlyingActor How?

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Pitfalls of IBA Deep and tangled hierarchies Diamond ring inheritance Copy-paste code here and there Special cases Magic: don’t touch it

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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”

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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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Don’t use CBA... yet CBA can’t save 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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Who Are Using Lua

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Advantages of Lua Lightweight Extensible Cross-platform Robust Openness Community

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Drawbacks of 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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Pitfalls of 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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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 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 = Container Widgets Button Render/Update Movement Scale Up/Down Fade In/Out Sprite Motion Transform Fade

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