How to read Lua table return value from C++

Question

I have a Lua function that returns table (contains set of strings) the function run fine using this code:

lua_pushstring (lua, "funcname");  
lua_gettable   (lua, LUA_GLOBALSINDEX);
lua_pushstring(lua, "someparam");
lua_pcall (lua, 1, 1, 0);

the function returns a table. How do I read it's contents from my C++ code?

Answer 1

If you are asking how to traverse the resulting table, you need lua_next (the link also contains an example). As egarcia said, if lua_pcall returns 0, the table the function returned can be found on top of the stack.

Answer 2

If the function doesn't throw any errors, then lua_pcall will:

1. Remove the parameters from the stack
2. Push the result to the stack

This means that, if your function doesn't throw any errors, you can use lua_setfield right away - lua_pcall will work just like lua_call:

lua_pushstring (lua, "funcname");  
lua_gettable   (lua, LUA_GLOBALSINDEX);
lua_pushstring(lua, "someparam");
lua_pcall (lua, 1, 1, 0);
lua_setfield(L, LUA_GLOBALSINDEX, "a");        /* set global 'a' */

would be the equivalent of:

a = funcname(someparam)