From: Robert Klemme <shortcutter@...>
Date: 2012-02-01T21:33:42+09:00
Subject: Re: Multiple assignment in conditional

On Wed, Feb 1, 2012 at 1:05 PM, Gavin Sinclair <gsinclair@gmail.com> wrote:
> On Wed, Feb 1, 2012 at 10:57 PM, Gavin Sinclair <gsinclair@gmail.com> wrote:
>
> Sorry to reply to my own message, but I thought of something I should
> have included.
>
> Here is the forbidden version I would like to write.  Obviously I'm
> combining assignment and conditional, which may not win plaudits as a
> general rule.
>
>>  def week_and_day(date)
>>    if not self.include? date
>>      return nil
>>    elsif (week, day = @t1.week_and_day(date))
>>      return [week, day]
>>    elsif (week, day = @t2.week_and_day(date))
>>      week += @t1.number_of_weeks
>>      return [week, day]
>>    end
>>  end
>
> But consider this alternative, where I separate the assignment and the
> conditional.
>
>  def week_and_day(date)
>    if not self.include? date
>      return nil
>    else
>      week, day = @t1.week_and_day(date)
>      if week
>        return [week, day]
>      else
>        week, day = @t2.week_and_day(date)
>        week += @t1.number_of_weeks
>        return [week, day]
>      end
>    end
>  end
>
> I consider this very clumsy.  By _not_ combining assignment with
> conditional, I cannot use "elsif".  I must split the "else" and the
> "if", and turn the second conditional into a child instead of a
> sibling.
>
> Definitely less intentional and unattractive code.

There are plenty more solutions, for example:

 def week_and_day(date)
   return nil unless include? date

   week_and_day = @t1.week_and_day(date) and return week_and_day

   week_and_day = @t2.week_and_day(date)
   week_and_day[0] += @t1.number_of_weeks if week_and_day

   week_and_day
 end

Maybe also

 def week_and_day(date)
   return nil unless include? date

   case
   when week_and_day = @t1.week_and_day(date)
     nil
   when week_and_day = @t2.week_and_day(date)
     week_and_day[0] += @t1.number_of_weeks
   end

   week_and_day
 end

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/