Re: Read only tables.

["Imagine Programming" <contact@...>]

I don't use table insert, i use the next local function plus the line below 
that.
local function c(t)
   local n=0;
   for i, v in pairs(t) do
       n=i;
   end
   return n;
end;
tValues[c(tValues)+1]="bla";   -- I use lua 5.0

Your idea about giving them their own table to mess with
is quite good, thank you. This spares me a lot of thoughts hehe.

I also will look into strict.lua. Thank you.

--------------------------------------------------
From: "Sam Roberts" <vieuxtech@gmail.com>
Sent: Wednesday, June 17, 2009 8:26 PM
To: "Lua list" <lua@bazar2.conectiva.com.br>
Subject: Re: Read only tables.

> On Wed, Jun 17, 2009 at 11:11 AM, Imagine
> Programming<contact@imagine-programming.com> wrote:
> > It's a lua plugin script that contains a table that should be only
> > changed through the plugin functions. If the user accidentally
> > changes the table it will mess up the functionallity of the plugin.
> >
> > most of these users are no programming experts, so I'd like to make it as
> > easy for them as i can.
>
> What about if they accidently redefine table.insert, will that effect
> you're plugin?
>
> > I havn't got much knowlege about setmetatable and getmetatable, so would
> > it be wise for me to just let this be and not make the table read only?
>
> If you need to sandbox them, you're going to have work harder, and
> identify what you don't want them to do (os.system(), io.popen()?).
>
> If its just this table you're worried about, and you want to make sure
> they don't change the real on, why not just make a copy of the table,
> and pass it to them. You're plugin can use the real one, they'll only
> mess up their copy.
>
> Personally, I think that if they can be trusted not to actually be
> malicious, then you might be best focussing on avoiding them making
> mistakes by giving them APIs to use that are so easy to use they don't
> make mistakes. If they keep doing lame things, you can focus on the
> stuff that ends up being a problem.
>
> And check out strict.lua, you might want to pre-require that to
> prevent them mis-typing names.
>
> Cheers,
> Sam
>
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