Re: String access & metamethods

[Stefan Sandberg <keffo.sandberg@...>]

One era ago I wrote an appender for lualogging for localization, with 
some trickery from sir Rici, which ended up being quite useful.

http://giger.servebeer.com/pics/Development/Lua/localizedAppender.zip

Sample follows:
----

   require "logging.localized"
   localizer = logging.localized( 'dictionary.swedish', logging.null() )
   print( localizedLog:info( { id='SomeIdentifier', SomeParam=1986 } ) )

and dictionary.swedish would look like this:


   module( ... )
   messages = {}
   messages.WhatHappenedThen = "På våren '${SomeParam}' brann mina 
termobyxor upp på en åker."


Brett Kugler wrote:
> I've been using Lua for a while now, but really have kept things 
> fairly simple as far as some of the more 'interesting' Lua features.
>
> I'm now attempting to implement localization to my Lua apps and 
> thought this would be a good time to look into using metamethods, as 
> the solution I've thought up seems to call for them.  Unfortunately, 
> I've never used them and what's more, I'm not sure what I'm attempting 
> can be accomplished even with that powerful tool in my pocket.
>
> So here's the skinny.  I would like every literal string reference the 
> VM encounters to be compared to a table of localized strings and 
> return either the localized version, or the original string if it's 
> not in the table.  Here's a quick code snippet (Lua 5.1):
>
> t={}
> t["english1"]={"english1","spanish1","french1"}
> t["english2"]={"english2","spanish2","french2"}
> t["english3"]={"english3","spanish3","french3"}
>
> language=2 -- Spanish
>
> print("english1")    <- spanish1
> a_word="english2"  <-  a_word="spanish2"
>
> function(in_string)
>     if t[in_string][language] ~= nil then
>         return t[in_string][language]
>     else
>         return in_string
> end
>
> So now the question.  How do I make the string access in 
> print("english1") trigger the metamethod of a string and which 
> metamethod would that be?  Since I also want this to be generic, it 
> really should work across any string access at any point in the 
> execution.  What I mean by this is that the triggering of the lookup 
> function should be tied to the string literal, not the function using 
> it ( foo("english1") should also return the result of the lookup 
> function.  How about statements like a_word="english1"?
>
> I realize I could simplify my life with a little extra notation, but 
> the hope was to really not change my existing code at all and have the 
> string literals be reinterpreted based on a new metamethod instead.  
> Am I grasping at straws?
>
> Thanks for any advice in advance,
> Brett