title: How do I add a different class to a div when iterating through a collection on each pass?
body: <p>This is what I want the end product to look like:</p>
  
  <pre><code>  &lt;div class="side-img top"&gt;&lt;%= image_tag product.image_url(:banner_thumb).to_s %&gt;&lt;/div&gt;
    &lt;div class="side-img mid"&gt;&lt;%= image_tag product.image_url(:banner_thumb).to_s %&gt;&lt;/div&gt;
    &lt;div class="side-img bottom"&gt;&lt;%= image_tag product.image_url(:banner_thumb).to_s %&gt;&lt;/div&gt;
  </code></pre>
  
  <p>Notice the 2nd class on each div changes for each <code>product</code>.</p>
  
  <p>So how do I cycle through this collection and dynamically apply each of those 3 classes so I will get the above result?</p>