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I'm trying to render a bulk of content in rows of three. However, I'm not sure how would I determine the current position of the element using Ruby. This is what I have:

<% Animals.each do | animal | %> <%= animal.species %> <% end %>

I want to be able to add a <BR> or if I was rendering a table a </TR><TR> each time we'd hit the third animal in the set. Of course, if the number of elements nE isn't divisible by three, then the table would be malformed. I figured by doing a bit of checking after the iteration that I could close it.

But is there a way to get the index of an element that's being iterated over in an Array.each method? I have the strong hunch that I could just do the following:

<table> <% Animals.each do | animal | %> <% if Animals.find_index(animal) / 3 == 0 %> <tr> <% end %> <td><%= animal.species %></td> <% if Animals.find_index(animal) / 3 == 2 %> </tr> <% end %> </table>

My only thing is that Animal is a subclass of ActiveRecord::Base, so I'm not sure (haven't looked to see) if this would scale well, let alone if each call to find_index would be a super intensive method. Any suggestions are welcome.

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  • I'm using Ruby 1.9.3 and according to apidock.com/ruby/Enumerable/Enumerator/each_with_index that method isn't available in that version. However, this would have done the job! Commented Jul 26, 2012 at 18:10
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    That method is available. It was only moved to a different part of Enumerable and since Array inherits from it, the method is still available to Array. Commented Jul 26, 2012 at 18:19

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You need 

<% animals = Animals.all %> <table> <% animals.in_groups_of(3) do |animal_row| %> <tr> <% animal_row.compact.each do |animal| %> <td><%= render animal %></td> <% end %> </tr> <% end %> </table>

Should roughly do the job.

More importantly, I think keeping the Enumerable module's documentation handy has been great for me as a Ruby developer. It is my "favourite" module, and nearly ALWAYS helps me solve tricky problems easily.

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Talk about a quick reply! Thanks!
Notice how i've used compact in the inner loop. It is critical becase that the last group of 3 may not contain exactly 3 elements (when the total elements are not divisible by 3). The last set is padded with nils and compacting the last sent saves you from nil errors.
I was going to ask why, but then you read my mind! Thank you again :D
I pre-empted your question :)
Not much of a difference but, animals.in_groups_of(3, false) will get rid of the extra nils so you won't have to use compact later.

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