Re: A Multi-User Dungeon (MUD) in Lua?

["Alex Davies" <alex.mania@...>]

Kurt Nordstrom wrote:
> One of my concerns here is security.  I want the master object to be able
> to arbitrarily call the game objects, but I don't want the game objects to
> be able to see or affect the master object.  Can anybody suggest a good
> way of doing this?  One possibility I thought was to possibly give all of
> the game objects a different environment, in which the master object would
> not be a part of.  The other would be to enact some sort of privacy scheme
> using closures like detailed in the Programming in Lua book.

If you just plan on having the one object, closures are the obvious choice. 
Just make sure the debug library isn't accessible, or at least not the 
debug.getupvalue / debug.setupvalue functions.

Closures are the obvious choice because, if you only have one object, you 
can simply do this:

mysuperobject = {}

do
 local privatetable = {}
 local privatevar
 function mysuperobject:func1()
   -- "public" variables / methods etc are simply
   mysuperobject.var1 = 1
   -- (or, if you're using the method syntax)
   self.var = 1
 end
 function mysuperobject:func2()
   -- "private" variables / methods can be accessed through upvalues, ie
   privatestate.var1 = 1
   privatevar = 1
   -- whether you keep all variables inside one "state" table or as a bunch 
of non-locals is up to you
 end
end

-- After this end, none of the locals inside the do..end block can be 
modified except for through function calls

It's ideal if you're planning on creating the object only once, as there's 
no need to share private states between multiple objects or create dozens of 
closures repeatedly.

Note, people can still modify mysuperobject, ie mysuperobject.func1 = nil.

- Alex