Scripting with Lua - Game Coding Complete - page 366

public:
void SetPosition(float x, float y, float z);
static LuaObject CreateFromScript(void); // new function on the Ninja class
};

LuaObject Ninja::CreateFromScript(void)
{

// create the C++ instance
Ninja* pCppInstance = new Ninja();

// create the Lua instance
LuaObject luaInstance;
luaInstance.AssignNewTable(pLuaState);

// assign the C++ instance pointer to the lua instance
luaInstance.SetLightUserData( “ __object ” , pCppInstance);

// assign the metatable to the new Lua instance table
LuaObject metaTable =
pLuaState->GetGlobalVars().GetByName(“NinjaMetaTable”);
luaInstance.SetMetaTable(metaTable)

return luaObject;

}
The CreateFromScript() function also needs to be registered to Lua.

LuaObject globals = pLuaState->GetGlobals();
globals.RegisterDirect( “ CreateNinja ” , &Ninja::CreateFromScript);

Now you can create instances of the Ninja class in Lua and call the SetPosition()
function just like you would any other Lua object.

ninja = CreateNinja()
ninja:SetPosition(10, 20, 30)
These two methods of function and object registration form the basis of the glue
between C++ and Lua.

Bringing It All Together
In this next section, I ll show you how to bring all of these components together to

form a cohesive scripting system. I

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ll show you how to manage the LuaState object
and initialize the scripting system, how to send events to and receive events from the
Event Manager, and how to write your own processes that run inside Lua. This sec-
tion builds on everything you ' ve learned in this topic so far.

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