From: "Peña, Botp" <botp@...>
Date: 2002-11-14T11:41:45+09:00
Subject: Re: Keyword arguments?

cool. I like Gavin's code below.
Is there a Ruby Tips/SampleCodes page?

Gavin's code is worth pasting :-)
..probably under Tips->Argument Processing->Gavin->Sample code...

Kind regards,
-botp

> Gavin Sinclair [mailto:gsinclair@soyabean.com.au] expounded:
> ...
> Amidst all the discussion of various ways of achieving 
> keyword arguments or similar, one really nice feature has 
> been overlooked: easy default arguments. Here is a 
> representation of code I've written recently.
> 
> class Recorder
>   def initialize(init_params={})
>     init = process_params(init_params)
>     @database = init[:DATABASE]
>     @user     = init[:USER]
>     @password = init[:PASSWORD]
>   end
> 
>   def Recorder.init_defaults
>     {
>        :DATABASE = "...",
>        :USER     = "...",
>        :PASSWORD = "...",
>     }
>   end
> 
>   def process_params(hash)
>     defaults = init_defaults()
>     # Guard user against invalid keys
>     hash.keys.each do |key|
>       raise "Key not supported: #{key}" unless defaults.has? key
>     end
>     defaults.update(hash)
>   end
> end
> 
> 
> Now,
>   Recorder.new  and
>   Recorder.new(:USER => "smith", :PASSWORD => "apple")
> will use the appropriate defaults, and
>   Recorder.new(:LOG_FILE => "x.log")
> will fail with a meaningful error message.
> 
> Further, if anyone wants to find out the defaults, they only 
> have to ask:
>   Recorder.init_defaults
> 
> I've been very happy with this, and see no need for Ruby to 
> adopt explicit keyword arguments.
> 
> Gavin
> 
>