Re: Hi and pushing existing UserData from pointer

[Chris Camacho <c.camacho@...>]

well I'm totally lost now...

cpBody *has* a metatable (__index is used for the methods) I even tried

char buf[40];
cpBody *bb = (cpBody *)lua_newuserdata(L, sizeof(cpBody));
lua_pushvalue(L,-1);
luaL_getmetatable(L, "cpBody");
lua_setmetatable(L, -2);

lua_pushstring(L,"__cpBody_ptrs");
sprintf(buf,"%ld\0",(long)bb);
lua_setfield(L,-2,buf);

luaL_getmetatable(L, "cpBody");
lua_setmetatable(L, -2);
return bb;


How am I missing your previous advice, are you able to
explain in a clearer manner?

how else would I index the cpBody* C pointer with the userdata instance
in a table called __cpBody_ptrs  ?

Thanks
Chris



Jerome Vuarand wrote:
> 2009/8/18 Chris Camacho <c.camacho@ntlworld.com>:
>   
> > > You can use lua_pushvalue to duplicate the reference to the userdata
> > > on the stack. Then you can save one in the weak table (with the light
> > > userdata key), and do whatever you want with the other one.
> > >       
> >  char buf[40];
> >  cpBody *bb = (cpBody *)lua_newuserdata(L, sizeof(cpBody));
> >  lua_pushvalue(L,-1);
> >  lua_pushstring(L,"__cpBody_ptrs");
> >  sprintf(buf,"%ld\0",(long)bb);
> >  lua_setfield(L,-2,buf);
> >
> >  luaL_getmetatable(L, "cpBody");
> >  lua_setmetatable(L, -2);
> >  return bb;
> >
> > what on earth does attempt to index a userdata value mean?
> >     
>
> You're calling lua_setfield (which is an indexing operation), with the
> parameter -2 pointing to the stack slot where you created the 'bb'
> userdata. Since that userdata has no metatable the indexing operation
> fails.
>
> I don't know if that lua_pushvalue call is supposed to reflect the
> previous advices I gave you, but if it is you are clearly misusing it.
>   


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