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Calling a Lua function from c++ every frame

Started by ishkabible Jun 9, 2010 at 4:48 PM 3 replies 2.2k views

Original Post

Jun 9, 2010 at 4:48 PM

ok so i'm a little fuzzy on how to do this, the function dose not need to return any thing. i'm confused on how lua_getglobal works, i want to use a function in Lua that i'm going to call "main_loop" but after a declare it as a global variable using get global how do i call it? i think i just use lua_call(L,0,0) since there are no return values or arguments. but i'm unsure thats why i'm asking.

Nanoha

Jun 9, 2010 at 4:54 PM

did you try it? what happened when you did?

I'd suggest taking a look at somehting like luabind if your planning on using lua alot, it makes all this (and more) really simple. Sooner you start using it, easier it'll all be.

ishkabible

Jun 9, 2010 at 5:02 PM

it said "PANIC: error in call to Lua API (attempt to call nil valuue)"

here is my test programs code:

#include <iostream>extern "C" {    #include "lua.h"    #include "lualib.h"    #include "lauxlib.h"}using namespace std;lua_State* L;void LuaPrint() { lua_getglobal(L, "PrintMsg"); lua_call(L, 0, 0);}int main(){    L = lua_open();    luaL_openlibs(L);    luaL_dofile(L, "foo.lua");    LuaPrint();    lua_close(L);    return 0;}

and here is the lua script:

function PrintMsg() {
io.write("ok this is how you will call it");
}

m_switch

Jun 9, 2010 at 5:41 PM

That's not valid Lua.

It should look like:

function PrintMessage()   io.write("...")end

You need to check the return value from luaL_dofile so you can catch these sorts of errors. Likely you'd want to use lua_pcall over lua_call and check its return value also.

ishkabible

Jun 9, 2010 at 5:50 PM

o oops, now it's working thank you. i guess i need to remember to shift gears from c++ to Lua, not C++ to some mixture between flash and Lua, any way thanks again

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