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Icebone1000

Binding living C++ object to Lua with Lunar

7 posts in this topic

Hello,

So say I have set up a class to work with [url="http://lua-users.org/wiki/CppBindingWithLunar"]Lunar[/url] .
My understanding is that Lunar make the class TYPE available to be created from a Lua script (Im not sure exactly).
What I want is to give my already created class object to the Lua script I will be running every frame ( that will be a coroutine call).

So resuming, I want my exposed class methods able to modify, from Lua script, my already created object on C++.

I dont know how to use/modify Lunar to accomplish that, anyone can give me a hand? Im having really hard times with that binding stuff. Edited by Icebone1000
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For godsake, how is your approach when you use lua scripts in your c++ game??? (NOT meaning only as description files, but like an AI decision make code)
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Here is a topic on passing a list of objects to Lua, not sure if it helps you.
http://stackoverflow.com/questions/837772/how-do-i-pass-a-list-of-objects-from-c-to-lua

However, why don't you use some more powerful binding solution, such as Luabind, or something else?
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[quote name='wqking' timestamp='1352687528' post='5000092']
Here is a topic on passing a list of objects to Lua, not sure if it helps you.
[url="http://stackoverflow.com/questions/837772/how-do-i-pass-a-list-of-objects-from-c-to-lua"]http://stackoverflow...s-from-c-to-lua[/url]

However, why don't you use some more powerful binding solution, such as Luabind, or something else?
[/quote]

I want to keep a lightweight package...see, thats what is good about lua...Im just figuring out that lua for games is actually a piece of crap, because if u need to include a goddam huge and overbloated package to use it for c++, than no, its not good, its not more light, not more fast, its only good if you will use it as youd use it for C.

luabind, is said slow by a dude I respect:
http://stackoverflow.com/questions/103347/how-do-you-glue-lua-to-c-code

swig seems more complicated them programming win32 sockets..

damn man, last time I had so much trouble in programming was with the god fucking damn fbx sdk

thanks for the link, I will give a try Edited by Icebone1000
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Heres my lua script:

[source lang="cpp"]-- prints formated string
function printf(...)
io.write( string.format( unpack( arg ) ) )
end

---------------

printf( 2 )

a = LuaAIAgent()

printf(a:Lua_GetHP())

-- till here it works, cause its creating a new agent

b = LuaAIAgent:Lua_GetCurrent() -- THIS IS WHAT I WANT, to get the agent from c++
-- b = a:Lua_GetCurrent() -- also doesnt work (this is just getting the this pointer of 'a' itself)

[/source]

This crashs (the above code ) (mem exception)
If I remove b = LuaAIAgent:Lua_GetCurrent() it works.

Heres my class:

[source lang="cpp"]class LuaAIAgent : public BulletAIAgent{

//------------------------------------------------------------------------
// Lua stuff
//------------------------------------------------------------------------
lua_State *m_pLua;
const char *m_szLuaScriptFilename;
lua_State *m_pAgentCoroutine;

public:
//------------------------------------------------------------------------
// Lua Binding Stuff
//------------------------------------------------------------------------
static const char className[];
static Lunar<LuaAIAgent>::RegType methods[];
private:
//------------------------------------------------------------------------
// Lua Script Exposed Methods
//------------------------------------------------------------------------

int Lua_GetCurrent( lua_State * L_p ){

// - no args -

// return this object

Lunar<LuaAIAgent>::push( L_p, this );
return 1;
}
...
const char LuaAIAgent::className[] = "LuaAIAgent";

Lunar<LuaAIAgent>::RegType LuaAIAgent::methods[] = {

LUNAR_DECLARE_METHOD(LuaAIAgent, Lua_GetCurrent),
LUNAR_DECLARE_METHOD(LuaAIAgent, Lua_Move),
LUNAR_DECLARE_METHOD(LuaAIAgent, Lua_Shoot),

LUNAR_DECLARE_METHOD(LuaAIAgent, Lua_GetHP),
LUNAR_DECLARE_METHOD(LuaAIAgent, Lua_GetNAmmunition),

LUNAR_DECLARE_METHOD(LuaAIAgent, Lua_AtMapPos),
LUNAR_DECLARE_METHOD(LuaAIAgent, Lua_NAmmosDropped),
LUNAR_DECLARE_METHOD(LuaAIAgent, Lua_GetAmmosDroppedList),

LUNAR_DECLARE_METHOD(LuaAIAgent, Lua_NextDirectionOnPathTo),
LUNAR_DECLARE_METHOD(LuaAIAgent, Lua_DirectionToAligned_AdjacentCell),
LUNAR_DECLARE_METHOD(LuaAIAgent, Lua_CloserDirectionToUnalignedCell),

{0,0} // sentinel
};

[/source]

--why its not highlithing the syntax ?- nevermind- Edited by Icebone1000
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What Id need is give to lua, trough something like a lua script global variable, the THIS pointer I have in c++, someone know how I can do this?
i.e.:
lua_pushObject( luaState, this );
lua_setGlobal( "aiAgentFromGameEngine", -1 );

the problem is that the lua script must still know that the object is the one registered by lunar (so I can use its methods)
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If you just want to set something to the this pointer, you can use light userdata. [url="http://www.lua.org/pil/28.5.html"]http://www.lua.org/pil/28.5.html[/url] Edited by patrrr
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I think I got it to work, finally, I feel It didnt even worth thou, so much time spent on hat .__.
I did it like that:
Inside my agent class:
[source lang="cpp"] //------------------------------------------------------------------------
// Lua Binding Stuff
//------------------------------------------------------------------------
static const char className[];
static Lunar<LuaAIAgent>::RegType methods[];
static LuaAIAgent* currentAgent;
static int push_object (lua_State* L){

Lunar<LuaAIAgent>::push(L, currentAgent, true);
return 1;
}[/source]
And then, on the constructor of my class I init the static pointer to the this pointer:

[source lang="cpp"] //------------------------------------------------------------------------
// ctor
//------------------------------------------------------------------------
LuaAIAgent( const char image_p, COLOR color_p, const Coord &amp; pos_p )
: BulletAIAgent(image_p, color_p, pos_p){

...

currentAgent = this;
}[/source]

Then theres this method:
[source lang="cpp"]void InitLuaScript( const char * szLuaScriptFilename_p ){


m_szLuaScriptFilename = szLuaScriptFilename_p;

// create a Lua state and register the exposed methods

m_pLua = lua_open();
luaL_openlibs(m_pLua);

Lunar<LuaAIAgent>::Register( m_pLua );

lua_pushcfunction(m_pLua, push_object);
lua_setglobal(m_pLua, "push_object");

// compile script

if( luaL_loadfile( m_pLua, m_szLuaScriptFilename ) != 0 ){

throw std::exception( "problem loading Lua script" );
}

// execute the file
int err = lua_pcall( m_pLua, 0, 0, 0 );
if( err != 0 ){

// 2 = runtime error
// 4 = mem alloc error

throw std::exception( "problem running Lua script" );
}
...
[/source]

And on the lua script:

[source lang="cpp"]b = push_object()

printf(b:Lua_GetHP())[/source]

Its lame, cause I can have only one agent, but its the only solution I got after uninterrupted 48 hours of researching and crying for help everywhere ( I dont know how I could store a bunch of static pointers and init them properly with the agents...naming the function differently would be easy and convenient (GetAGentSmith, GetAgentDumb..) ) Edited by Icebone1000
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