book

Creating Solid APIs with Lua

by Tyler Neylon

February 2017

Intermediate to advanced

133 pages

2h 43m

English

O'Reilly Media, Inc.

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Acknowledgments
An Overview of the C/Lua InterfaceAn Example: EatyGuyGetting the Lua SourceIf You’re Using macOS or Linux…If You’re Using Windows…This Book’s GitHub RepoRunning a Lua Script from CLua Modules and Loading Them from CDrawing MazesOne Way to Call a Lua Function from CStack IndexesGiving Lua the Power of C
EatyGuy Version 1: A Lua-Callable C FunctionThe tput Shell CommandThe Core Mechanics of Lua-Callable C FunctionsEatyGuy Version 2: Adding an Animated PlayerStrings and Multiple Arguments with set_color() and set_pos()Sending a Return Value from C to Lua by Using timestamp()Fancier Maze DrawingStarting, Stopping, and Sharing Functions with LuaGame State and Lua’s Event LoopUpdating Player StateDrawing the Player StateCalling Lua Functions from C More Effectively
EatyGuy Version 3: Passing Data to a Lua FunctionReceiving Arrow Key PressesEatyGuy Version 4: Implementing API Functions Within LuaFixing the tput BottleneckEatyGuy Version 5: Working with Lua Tables from CWhere Tables LiveThe Primary Table FunctionsUsing a Table to Send Game State to LuaAdding Some Class to Your API
EatyGuy Version 6: Writing a Class in LuaA Common Code Pattern for Lua ClassesThe Character Class ExampleEatyGuy Version 7: Class InheritanceSubclasses in LuaThe Baddy ClassEatyGuy Version 8: Introducing the userdata TypeWriting a Lua-Loadable Module in CImplementing a Class-Like userdata TypeIntegrating a C Module into Your APIMaking Your Code Debug-Friendly
Throwing and Catching Errors in LuaWhen Should You Throw an Exception?Don’t Panic!Lua Errors in CHow lua_pcall() Handles ErrorsTurtles All the Way DownGetting Strict About Globals and TyposThe Environment of Freshly Loaded ChunksA Version of strict.luaEatyGuy Version 9: Death, StrictlyA Brief but Quickly Dismissed Question of Morality
EatyGuy Version 10: The Baddy Construction KitThe Code of Scum and VillainyScripts Gone WildControlling Library AccessManaging Memory UseManaging CPU UseEnd == Nigh

Content preview from Creating Solid APIs with Lua

Chapter 4. Making Your API Classy

Often, the functions in an API can be broken down into a few categories. Suppose, for instance, that a library allows you to manage both image files and movie files. In cases like this, it’s natural to use a class to represent each conceptual object or task being performed by a subset of the interface—for example, we could have an Image class and a Movie class. This chapter covers common methods of defining classes in Lua; implementing inheritance; and defining custom, class-like userdata types in C.

EatyGuy Version 6: Writing a Class in Lua

Most of Lua’s design is simple and transparent, including the building blocks of Lua’s class system. Nonetheless, Lua does ask for some depth of thought when it’s time to implement classes and class inheritance. This is due to the fact that classes in Lua are not directly supported by the language; rather, they are enabled by giving coders the low-level pieces needed to be assembled into class mechanics. Because of this, I’ll cover Lua classes in more detail than I’ve previously covered other language features.

In this chapter, we add enemies to EatyGuy. Let’s call them baddies because it sounds more fun. This is a great opportunity to implement a class–subclass relationship: the player and baddies can share a common superclass that we’ll call Character, whereas the baddy-specific behavior will live in subclass called Baddy. As is common in some languages, we’ll capitalize the names of classes and class-like ...