From: "Nigel S.Ball" <nigelb@...>
Date: 2001-10-22T13:22:59+09:00
Subject: [ruby-talk:22930] Re: Configuration class

As usual I have answered one of my questions myself!

On Mon, 22 Oct 2001 12:15, you wrote:
> I would like some thoughts on a question that I am trying to resolve.
>
> I have an application which is longrunning but needs to create a separate
> environment to eal with different states. This means that I really don't
> want globals and global constants apart from those which apply to all
> states. I also hate typing and want to be able to create the environments
> for each state easily. Ultimately I want to be able to load the config from
> a file.
>
> Starting from here
> $GLOBALCONSTANT = 'GLOBALCONSTANTVALUE'
> $globalhash = {"gh1"=>"gv1", "gh2"=>"gv2"}
>
> I have thought of the following
>
> 1. Create a Hash containing all the constants
> gv = {'GLOBALCONSTANT '=> 'GLOBALCONSTANTVALUE',
> 	'globalhash' => {"gh1"=>"gv1", "gh2"=>"gv2"}
>         }
>
> This is admittedly simple but, to me at least, is not very pretty. To
> access a value we have gv['GLOBALCONSTANT']
>
> 2. Convert the Hash from thought 1 into a class (lifted from cgi.rb)
> class Config
>   def initialize(hash={})
>     @hash = hash
>     hash.each {|key, val|
>       eval( <<-END )
>         def #{key.downcase}
>           "#{val}"
replace this line with
	#{val.inspect}
>         end
>       END
>     }
>   end
> end
>
> cfg = Config.new(gv)
>
> This is somwhat more elegant as variables are accessed by
> cfg.globalconstant However, as it stands it can only be used for strings.
> Can anyone tell me how to deal with other objects?

I can answer this myself now ... use value.inspect
>

> 3 Use a Struct to hold the values
> Config = Struct.new("Config", :globalconstant, :globalhash)
> cfg = Config.new('GLOBALCONSTANTVALUE', {"gh1"=>"gv1", "gh2"=>"gv2"})
>
> This seems to have the advantages of 2 but suffers from the need to set the
> names of the elements and their values separately. The values are, in fact
> set by position, very ugly IMHO.
>
> I guess what I would really like is a class which when passed a hash
> returns the equivalent Struct with the values set accordingly.
>
> Any thoughts or suggestions would be appreciated.

-- 
Nigel S. Ball
Enesbe Sales Pty Ltd
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