RE: metatable and c++ assistance/thoughts

["Kevin Baca" <lualist@...>]

You said you were using a *light* userdata.

The boxpointer macros create a *heavy* userdata.

You can't receive a gc event on a table and the only way to receive a gc
event on a userdata is if it's a heavy userdata.

-Kevin

> -----Original Message-----
> From: lua-bounces@bazar2.conectiva.com.br 
> [mailto:lua-bounces@bazar2.conectiva.com.br] On Behalf Of 
> Robert Sadedin
> Sent: Monday, October 18, 2004 11:30 PM
> To: lua@bazar2.conectiva.com.br
> Subject: RE: metatable and c++ assistance/thoughts
> 
> 
> Thanks Kevin.  That's what I'm doing, except I'm not using 
> the macros, 
> rather calling the methods directly.
> 
> Am I missing something, or wouldn't it be nice to be able to 
> garbage collect 
> a table from c++ as well as userdata?
> 
> >The only way to receive a __gc event on a user data is to 
> make it a full
> >user data with a metatable that contains a __gc metamethod.
> >
> >A relatively lightweight way to do this is to use Lua's 
> "boxpointer" set
> >of macros.
> >
> ><code>
> >     lua_boxpointer( L, my_pointer);
> >     lua_newtable( L );
> >     lua_pushstring( L, "__gc" );
> >     lua_pushcfunction( L, myGCFunction );
> >     lua_settable( L, -3 );
> >     lua_setmetatable( L, -2 );
> ></code>
> >
> ><code>
> >int myGCFunction( lua_State* L )
> >{
> >     MyData* my_pointer = ( MyData* ) lua_unboxpointer( L, 1 )
> >
> >     delete my_pointer;
> >}
> ></code>
> >
> >-Kevin
> >
> > > -----Original Message-----
> > > From: lua-bounces@bazar2.conectiva.com.br
> > > [mailto:lua-bounces@bazar2.conectiva.com.br] On Behalf Of
> > > Robert Sadedin
> > > Sent: Monday, October 18, 2004 7:53 PM
> > > To: lua@bazar2.conectiva.com.br
> > > Subject: metatable and c++ assistance/thoughts
> > >
> > >
> > > Hi all,
> > >
> > > I'm trying to work with objects in both lua and c++, and am
> > > playing with
> > > creating a table from c++ with static methods from c++ linked
> > > into table
> > > functions, and a pointer to the c++ object stored in the
> > > table with some
> > > appropriate name (this, for instance).
> > > Then, when a table method is called with the : operator, 
> the table is
> > > passed,  I can extract the pointer, and everything is groovy
> > > then to call
> > > the object from c++.
> > >
> > > I want to control the garbage collection on the object,
> > > though, since at
> > > present it leaks terribly because the garbage collector
> > > doesn't fire on the
> > > lightuserdata I'm storing the pointer as.
> > >
> > > I can make it a userdata, and specifically create it and add
> > > a metatable to
> > > it for __gc, but I'd rather not have to.
> > >
> > > Is there anyway I can control destruction of a table (appears
> > > not from the
> > > manual)?  Perhaps people can very quickly say I'm simply a
> > > fool for thinking
> > > of managing things in the manner I've set out ... ?
> > >
> > >
> > >
> > > Rob
> > >
> >
>