From: Eleanor McHugh <eleanor@...>
Date: 2009-06-12T21:15:34+09:00
Subject: Re: Idiomatic way to detect first/last iteration?

On 12 Jun 2009, at 12:45, paron wrote:
> Is detection really what you want? Doesn't that imply that you test
> each iteration? Since the array is ordered by definition, it seems
> (needs tested!) that creating three entities might be faster.
>
> in helper:
> def first_also_ran_last(records)
>
>  first_record=records.shift
>  last_record=records.pop
>
>  return [first_record, records, last_record]
> end
>
> in view:
> <% parsed_records = first_also_ran_last(@whatever)
> <%="Really like #{parsed_records[0]}"%>
> <% parsed_records[1].each do |also_ran|%> #(if any)
>  <%= "Sorta like #{also_ran}"%>
> <%end -%>
> <%unless parsed_records[2].nil?-%>
>  <%= "Don't much like #{parsed_records[2]}"%>
> <%end->
>
> Don't know if it's faster, or more idiomatic, but perhaps it's more
> semantic?

With a bit of tidying you can reduce the view further:

	def x records, message = "Nothing Relevant"			# I can't think of a  
_good_ name for the method off-hand
		first = records.shift || message
		last = records.pop || message
		[first, records.empty? ? [message] || records, last]
	end

	<%	track_listing = x records, "I don't have one!!!"	%>
	<%=	"My favourite track: #{track_listing.shift}		%>
	<%	track_listing.shift.each do |track|	-%>
	<%=		"Another track I like: #{track}	%>
	<%	end	-%>
	<%=	"The track I like least: #{track_listing.shift} %>


Ellie

Eleanor McHugh
Games With Brains
http://slides.games-with-brains.net
----
raise ArgumentError unless @reality.responds_to? :reason