Rails 4.0 every 3 each div loops then applying class

Question

I have looping here below

- @published_only.each do |p|
  .movie.effect
    = image_tag(p.poster_url(:thumb), class: "img")
    .mini-desc
      %h4= p.title

it will give

<div class="movie effect>...</div>
<div class="movie effect>...</div>
<div class="movie effect>...</div>
<div class="movie effect>...</div>
<div class="movie effect>...</div>
<div class="movie effect>...</div>

How to make it going to apply 'last' class for every 3 div. for example:

<div class="movie effect>...</div>
<div class="movie effect>...</div>
<div class="movie effect last>...</div>
<div class="movie effect>...</div>
<div class="movie effect>...</div>
<div class="movie effect last>...</div>

Answer 1

You can use cycle method:

.movie.effect{class: cycle('', '', 'last')}