From: Robert Klemme <shortcutter@...>
Date: 2011-10-10T18:46:58+09:00
Subject: Re: assigning session hash to a variable doesn't keep modified hash in session

On Sun, Oct 9, 2011 at 11:28 PM, John Merlino <stoicism1@aol.com> wrote:
> Hey all,
>
> I basically have some nested hashes stored in the session variable:
>
> def set_code(unit_id, code)
>
>     if session[:code].select {|h| h[unit_id]}.empty?
>       session[:code] << { unit_id => {}}
>     end
>
>      case code
>      when 3,4
>        session[:code].detect {|h| h[unit_id]}[unit_id][:code_a] ||= []
>        session[:code].detect {|h| h[unit_id]}[unit_id][:code_a] << code
>      when 8,9
>        session[:code].detect {|h| h[unit_id]}[unit_id][:code_b] ||= []
>        session[:code].detect {|h| h[unit_id]}[unit_id][:code_b] << code
>      end
>  end
>
>
> From the code above, you can see four lines of repetitive code. The
> problem is if I did this:
>
> unit_hash = session[:code].detect {|h| h[unit_id]}[unit_id]
>
> case code
> when 3,4
>  unit_hash[:code_a] ||= []
>  unit_hash[:code_a] << code
> when 8,9
>  unit_hash[:code_b] ||= []
>  unit_hash[:code_b] << code
> end
>
> Then the appended code will not be stored in the session.
>
> Any way to refactor this so I dont have 4 repetitive lines of code?

Put the result of repetitive code in a variable.  This might do the same:

def set_code(unit_id, code)
  s_code = session[:code]
  unit_id_hash = s_code.detect {|h| h[unit_id]}

  if unit_id_hash.nil?
    unit_id_hash = {}
    s_code << {unid_id => unit_id_hash}
  end

  # this lookup could be done via a constant Hash as well
  key = case code
    when 3,4
      :code_a
    when 8,9
      :code_b
    end

  unit_id_hash[key] << code if key
end

But frankly, your data structure looks suspicious to me.  For example:
why is session[:code] an Array containing of Hashes with only one key
value pair?  Why don't you make it a Hash where indexed by code?

Kind regards

robert

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