How to determine last object in each loop?

Question

In your typical each loop in Rails, how do I determine the last object, because I want to do something different to it than the rest of the objects.

<% @stuff.each do |thing| %>

<% end %>

score 66 · Answer 1 · answered Feb 13 '13 at 09:12

66

@stuff.each do |s|
  ...normal stuff...
  if s == @stuff.last
    ...special stuff...
  end
end

answered Feb 13 '13 at 09:12

abject_error

2

this is the best answer... could be a touch better if you'd like to 1-line it. `s == @stuff.last ? 'thing for last' : 'things for the rest'` – Dudo Oct 01 '13 at 01:34
15

warning: this won't work if @stuff elements aren't unique. ie "a = [1,1];a.map{|v| v == a.last}" returns [true,true]. in case of integers there's no way to determine if it's really last element. if using other objects, you can use equal? (http://stackoverflow.com/questions/7156955/whats-the-difference-between-equal-eql-and) – Pavel K. Dec 03 '13 at 15:11

score 33 · Answer 2 · edited Jun 13 '12 at 18:13

33

Interesting question. Use an each_with_index.

len = @stuff.length

@stuff.each_with_index do |x, index|
 # should be index + 1       
 if index+1 == len
 # do something
  end
end

edited Jun 13 '12 at 18:13

Jakub Kuchar

answered May 30 '09 at 06:43

A.Ali

1

I find `if index == len + 1` more aesthetic. – Benjamin J. Benoudis Apr 12 '15 at 04:11
isn't it suppose to be @stuff.each_with_index do |index, x|? (first the object and then the index) – Stefanos.Ioannou Feb 01 '16 at 10:50
7

@BenjaminBenoudis that would be `if index == len - 1` – andreofthecape Oct 28 '16 at 06:45

score 8 · Answer 3 · answered Feb 13 '13 at 09:04

8

<% @stuff[0...-1].each do |thing| %>
  <%= thing %>
<% end %>
<%= @stuff.last %>

answered Feb 13 '13 at 09:04

jackpipe

Much nicer than checking every iteration if we're at the end! Although I think you have one too many `.`'s? – Matt Aug 31 '16 at 14:06
Thanks! Actually it's a little confusing, since `-1` in a range stands for "the last element", so actually `stuff[0..-1] == stuff`. We need to use the `...` form of range which omits the last element. – jackpipe Jan 12 '17 at 06:48
I see! You should add that to the answer to make it a bit clearer and save stupid questions like mine ;) – Matt Jan 12 '17 at 14:48

score 2 · Answer 4 · answered May 30 '09 at 06:44

2

A somewhat naive way to handle it, but:

<% @stuff.each_with_index do |thing, i| %>
  <% if (i + 1) == @stuff.length %>
    ...
  <% else %>
    ...
  <% end %>
<% end %>

answered May 30 '09 at 06:44

apostlion

score 2 · Answer 5 · answered Jun 01 '09 at 20:37

2

A more lispy alternative is to be to use

@stuff[1..-1].each do |thing|

end
@stuff[-1].do_something_else

answered Jun 01 '09 at 20:37

Sam

5 Answers5