From: Robert Klemme <shortcutter@...>
Date: 2008-02-01T00:06:23+09:00
Subject: Re: can ik make this more beautifull?

2008/1/31, Jari Williamsson <jari.williamsson@mailbox.swipnet.se>:
> Peter Hickman wrote:
> > Jari Williamsson wrote:
> >> Remco Hh wrote:
> >>> nowadays i try to improve my coding style to produce nicer and beter
> >>> readable code. I try to improve the following code but i dont know how.
> >>>
> >>> if condtion1
> >>>       x=1
> >>>     else
> >>>       if condition2
> >>>          x=2
> >>>       else
> >>>          if condition3
> >>>            x=3
> >>>         end
> >>>       end
> >>>       x=nill
> >>>   end
> >>>
> >>> there are three different conditions which can not occur at the same
> >>> time
> >>> can i make this nicer?
> >>
> >> A case expression is probably the most clear alternative. The shortest
> >> is perhaps something like:
> >>
> >> x = condition1 ? 1 : condition2 ? 2 : 3
> >>
> >>
> >> Best regards,
> >>
> >> Jari Williamsson
> >>
> >>
> > Short it may be but this sort of code can hardly be called beautiful, I
> > have had to maintain crap like this before and the few keystrokes the
> > author saved was made up for 1000 times when someone updated it and
> > things didn't 'quite' work how they thought. Ruby allows simplicity and
> > clarity, this however is heading into obfuscation.
> >
> > The better solution is to use the elsif keyword to flatten the indentation:
> >
> > if (temp == 'cat')
> >  x = 1
> > elsif(temp == 'dog')
> >  x = 2
> > elsif(temp == 'banana')
> >  x = 3
> > else
> >  x = nil
> > end
>
> But this elsif solution isn't heading for clarity either, compared to
> using a case expression:
> x = case temp
>          when 1 then 'cat'
>          when 2 then 'dog'
>          when 3 then 'banana'
>          else nil
>      end
>
> In the elsif example, x appears 4 times instead of 1, temp appears 3
> times instead of 1. Apart from require an editor that support
> refactoring and the risk of typos, there will also be a performance hit
> when temp isn't matched.

If you are using "case" then there is yet another solution:

x = case
  when condition1 then 1
  when condition2 then 2
  when condition3 then 3
  else nil
end

Another approach would be to stuff conditions in an array:

CONDITIONS = [
  lambda {|x| condition1 },
  lambda {|x| condition2 },
  lambda {|x| condition3 },
]

def test(*values)
  CONDITIONS.each_with_index do |c,i|
    return i+1 if c[*values]
  end
  nil
end

x = test "whatever"

Kind regards

robert

-- 
use.inject do |as, often| as.you_can - without end