Question

I need a very simple c++ function that calls a lua function that returns an array of strings, and stores them as a c++ vector. The function can look something like this:

std::vector<string> call_lua_func(string lua_source_code);

(where lua source code contains a lua function that returns an array of strings).

Any ideas?

Thanks!

Answer 1

Here is some source that may work for you. It may need some more polish and testing. It expects that the Lua chunk is returning the array of strings, but with slight modification could call a named function in the chunk. So, as-is, it works with "return {'a'}" as a parameter, but not "function a() return {'a'} end" as a parameter.

extern "C" {
#include "../src/lua.h"
#include "../src/lauxlib.h"
}

std::vector<string> call_lua_func(string lua_source_code)
{
  std::vector<string> list_strings;

  // create a Lua state
  lua_State *L = luaL_newstate();
  lua_settop(L,0);

  // execute the string chunk
  luaL_dostring(L, lua_source_code.c_str());

  // if only one return value, and value is a table
  if(lua_gettop(L) == 1 && lua_istable(L, 1))
  {
    // for each entry in the table
    int len = lua_objlen(L, 1);
    for(int i=1;i <= len; i++)
    {
      // get the entry to stack
      lua_pushinteger(L, i);
      lua_gettable(L, 1);

      // get table entry as string
      const char *s = lua_tostring(L, -1);
      if(s)
      {
        // push the value to the vector
        list_strings.push_back(s);
      }

      // remove entry from stack
      lua_pop(L,1);
    }
  }

  // destroy the Lua state
  lua_close(L);

  return list_strings;
}