Re: Need some help to use TFUNCTION
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- Subject: Re: Need some help to use TFUNCTION
- From: Sean Conner <sean@...>
- Date: Tue, 2 Jun 2015 22:42:50 -0400
It was thus said that the Great Laurent FAILLIE once stated:
> Hello,
> I'm working on a C programs using Lua as embedded language.
> At Lua side, I'm defining a table on witch a filed need to be a function as :
> _, err = Broker:subscribe {
> { topic = "/tata", function = myfunc },
> { topic = "tutu", function = func2 }}
> And I know at C side I have to look up for TFUNCTION for "function" field.My reading function is creating a structure containing
> - a string, the topic,
> - and a "reference" or something to keep track of the function
>
> now my question :1/ How can I store TFUNCTION at C side ?2/ How my C code can "call" this Lua function ?
> If it's not so clear, please have a look on my code here : https://github.com/destroyedlolo/Selene/blob/master/src/MQTT.c
> especially on line 79.
> Thanks
> Laurent
There are a few ways to do this. The easiest way is to store it in a
global variable in the Lua state:
static int foo(lua_State *L)
{
luaL_checktype(L,1,LUA_TFUNCTION);
lua_pushvalue(L,1); /* make sure it's at the top of the stack */
lua_setglobal(L,"myreffunction");
return 0;
}
And to call it:
static int bar(lua_State *L)
{
lua_getglobal(L,"myreffunction");
lua_call(L,0,0); /* no parameters */
return 0;
}
Another way is to store a reference in the Lua Registry:
int myfuncref;
static int foo(lua_State *L)
{
luaL_checktype(L,1,LUA_TFUNCTION);
myfuncref = luaL_ref(L,LUA_REGISTRYINDEX);
lua_pushinteger(L,myfuncref);
lua_pushvalue(L,1);
lua_settable(L,LUA_REGISTRYINDEX);
return 0;
}
And to call that:
static int bar(lua_State *L)
{
lua_pushinteger(L,myfuncref);
lua_gettable(L,LUA_REGISTRYINDEX);
lua_call(L,0,0);
return 0;
}
Personally, I would store a reference in the Lua Registry as it won't
pollute the global space.
-spc (This should be enough to get you started)