From: Robert Klemme <shortcutter@...>
Date: 2008-06-11T20:41:15+09:00
Subject: Re: each with else

2008/6/11 Thorsten Müller <thorsten@80beans.com>:
> Hi all,
>
> that's just an idea I came up with and thought worth a discussion.
>
> Would it be possible to give each an else part?
>
> For Rails programmers it is very common to do something like this:
>
> In controller search for records:
>
> @orders = Order. find(:all)
>
> In view:
>
> <% unless @orders.empty? then %>
>  <%   @orders.each do |order| %>
>    <%= output order somehow %>
>  <% end %>
> <% else %>
>  output message, that there are no orders
> <% end %>
>
> If each would have it's own else which runs if the
> used array, enumerable or whatever is empty,
> that code could look much nicer:
>
> <% @orders.each do |order| %>
>    <%= output order somehow %>
> <% else %>
>  output message, that there are no orders
> <% end %>
>
> I guess, that would be true for any other Ruby code, too.

No.  This does not work because your bit translates to

@orders.each do |order|
# output order somehow expression
else
end

This would mean that the "else" branch is executed for each iteration
because it is *inside* the block.  This is something you clearly do
not want.

> Please give your opinions to that idea and if you think
> there would be a chance to get this implemented one day...

I'd go with Robert's suggestion:

<% @orders.each do |order| %>
   <%= output order somehow %>
 <% end.empty? and begin %>
 output message, that there are no orders
<% end %>

or

<% if @orders.each do |order| %>
   <%= output order somehow %>
<% end.empty? %>
 output message, that there are no orders
<% end %>

Note that depending on the type of @orders you do not even need to
define #empty? (Array and Hash have it).  If there are special types
you could do

module Enumerable
  def each_checked
    found = false

    each do |item|
      found = true
      yield item
    end

    found
  end
end

and then

<% unless @orders.each_checked do |order| %>
   <%= output order somehow %>
<% end then %>
 output message, that there are no orders
<% end %>

Note: "then" is optional.

Kind regards

robert

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