Fio:LuaBinder

From Fio

"Like a bridge over troubled water..." - Simon and Garfunkel

still in ctoring

Contents 1 Lua Binder 1.1 Quick Tour 1.2 The Lua Application Program Interface 1.3 Construct An Object 1.4 Method Invoking 1.4.1 from lua into c++ 1.4.2 from c++ into lua 1.5 Type Checking 1.5.1 LSP 1.6 Destruct & Object Lifetime in the 2 Worlds 1.7 Misc

Lua Binder

Fio use Lua as scripting language to implement the game logic which include(in a broad sense):

• UI design and switching
• event handler
• combat scheduler
• npc behavior

All the logics/policies are build on the mechanisms carried out by c++ classes which will do the real work of rendering, timing, event dispatching etc. This separation is to make the game fully data driven - thru scripting the logic itself is taken as data which can be easily modified without the re-compile-link of the mechanism part(or the engine).

Lua has provided a bunch of APIs for "the host program to communicate with Lua". To call function from lua into c++, we have to:

• extract the arguments from lua stack;
• check the argument/return value type;
• call c++ function;
• push the return value onto lua stack;
• take care the return value's lifetime.

thru Lua APIs.

As the number of classes needs to be embedded into lua increases, these routine work will be a burden to write and maintain for each function call. There're quite a few binders out there to make the embedding easier. In Fio we implement a home brew binder - LuaUtil as a bridge between the c++ and lua world.(Not-Invented-Here Syndrome? no, it's just for better understanding of the scripting and faster compiling speed)

Quick Tour

The Lua Application Program Interface

Construct An Object

• normal
• lightweight

Method Invoking

• method wrap

from lua into c++

• traits
• Overload

from c++ into lua

callback?

Type Checking

LSP

Destruct & Object Lifetime in the 2 Worlds

Misc

• const
• panic
• utility functions