From: Phrogz <phrogz@...>
Date: 2007-11-25T00:05:00+09:00
Subject: Re: Extending to an existing case menu

On Nov 24, 4:23 am, Marc Heiler <sheve...@linuxmail.org> wrote:
> user_input = $stdin.gets.chomp
>
> case user_input
> when 'x'
>   puts 'this is a test'
> end
>
> # So far so fine. Now I want to add something like
>
> when 'y'
>   puts 'yay, a new test'
> end
>
> What would be the simplest or most elegant way?
> A hash with key -> action ?

The simplest, most elegant way, would be to just type it into the same
case code :)

If you want to be able to define the (arbitrary) results of a
comparison separate from the comparison itself, I think you need to
use blocks/procs. A Hash would certainly be a good way to store this,
assuming a simple case-like #=== comparison is all you need.

However, the syntax of defining a Hash of procs may not be the most
ideal, depending on your scenario. I might use a method wrapper like
so:

class ConditionMapper
  def initialize
    @conditions = {}
  end
  def when( *conditions, &action )
    conditions.each{ |condition| @conditions[ condition ] = action }
  end
  def check( obj )
    @conditions.each{ |condition,action|
      if condition === obj
        return action[ obj ]
      end
    }
  end
end

english_match = ConditionMapper.new
english_match.when( 1..5 ){ |x|
  puts "#{x} is between one and five"
}

english_match.when( 7, 42 ){ |x|
  puts "#{x} is a cool number"
}


english_match.check( 4 )
#=> 4 is between one and five

english_match.check( 42 )
#=> 42 is a cool number



> Only problem is that the action could be invoking a method or creating
> an object etc... and i dont want to use proc or lambda's at all.

Why not?