RE: LUA <--> C++ question

["Ashley Fryer" <lua@...>]

> I would like to enable communication between LUA and C++ classes. I don't
> want to use "tolua" or any other tool.
>
> Considere the following code, do you think these is a good way (or almost
> quite right) or do you think I was lucky not to have test.exe crashing ?
> Is there a way to simplify the whole operation ?

I use a similar approach in my code.  If you plan to use polymorphism, I
suggest you implement a common base class for all of your lua-enabled C++
classes.  Then make sure you always cast to the base class before
lua_pushuserdata.

Example:

class Scripted {};
class MyFoo : public Scripted {};

...

MyFoo my_foo;
lua_pushuserdata( static_cast< Scripted * >( & my_foo ) );

...

This also makes it possible to use dynamic_cast when you're going in the
other direction:

Scripted * my_scripted = (Scripted*)lua_getuserdata(lua_getparam(1));
MyFoo * my_foo = dynamic_cast< MyFoo * >( my_scripted );
if( my_foo )
{
// yes, we really have a MyFoo object...
}

These techniques will help you avoid some subtle bugs resulting from casts,
especially if any of your classes use multiple inheritance.

Other possibilities... you could implement a class with overloaded insertion
operators as syntactic sugar for the lua_pushXXX functions.  Then you could
do this:

LuaStack() << my_num << my_string;

Instead of:

lua_pushnumber( my_num );
lua_pushstring( my_string );


ashley