Checking type of userdata in C++

["Zé Pedro" <zarroba@...>]

Hi, I have a method in C++ accessible from Lua that receives an userdata object as a parameter. But it can receive one of several userdata types.
If I could get the string that I used when the metatable was created (luaL_newmetatable(pLuaState, "
Zara.sound");) I could compare it, but I can't find a way to do it.
Consider the following example:

int LObject::setRepresentation(lua_State* pLuaState)
{
    try 
    {
        //In here I'm trying to get the field were the userdata type is set (I thought that this could be a way to do it)
        cout << "--------------------------------" << endl;
        cout << lua_objlen(pLuaState,1) << endl;    //It returns 4 so I thought one of the positions would be the type
        cout << "-" << endl;
        lua_rawgeti(pLuaState,1,1);    //in what position is it?
        
cout << type = lua_tostring(pLuaState,-1) << endl;
        cout << "--------------------------------" << endl;
            
        Representation* rep = static_cast<ZMaterial*>(luaL_checkudata(pLuaState,3,"Zara.representation"));     //

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