From: Michael Fellinger <m.fellinger@...>
Date: 2007-10-17T08:37:08+09:00
Subject: Re: Compound conditionals in case when statements? Syntax?

On 10/17/07, Randy Kramer <rhkramer@gmail.com> wrote:
> I need (or want ;-) to do something like the following:
>
> when ((/^---\+\+ (.*)/) and (new_record == true))
>
> I've tried a lot of variations, but either this just won't work, or I haven't
> managed to guess the proper syntax.  (I've also tried googling and searching
> in the pickaxe(2).)
>
> Aside: Maybe the compound won't work because one is what the pickaxe calls a
> condition and the other is a comparison?  But, I'm not sure which is which.
>
> If this can't work, I'll try (I've been trying) a nested if statement, but
> I'll ask about that in my next post. ;-)

this can't work for the simple reason that the objects given at 'when'
are being sent the === message with the object in 'case'. In your
'when' it's the result of the stuff in closures.
This generally is the job of 'if', just keep in mind that case/when is
for matching, if/else is for conditionals.
One roundabout way exists to make this work though:

class Proc
  def ===(obj)
    self[obj]
  end
end

case 'foo'
when lambda{|e| new_record and /^---\+\+ (.*)/ === e }
  puts :aye_match
else
  puts :sorry_you_lose
end

This is generally only advised if your middle name is some form of
(Advent|Dang)erous, I won't be able to take responsibility for all
resulting damage. But also note that new_record being true or false
makes it simple to work with it without first comparing true/false
with true, the result won't change, true cannot become any more true.

a = true
# true
puts "hey" if a == true
hey
# nil
puts "hey" if a
hey

Hope this helps a little bit. Have fun with ruby!

^ manveru