Rails view to list users in a zebra-striped table

Question

<% i = 0 %> 
<% @patients.each do |patient| %> 
 <tr class="<%= i % 2 == 0 ? 'Even' : 'Odd' %>">
 <td><%= link_to patient.id, patient %></td>
 <td><%= patient.user.username %></td>
 <td><%= patient.user.first_name %></td>
 <td><%= patient.user.last_name %></td>
 <td><%= patient.user.email %></td>
 <td><%= patient.user.active %></td>
 <td><%= patient.user.disabled %></td>
 <td>
 <ul class="Horizlist">
 <li><%= link_to 'Detail', patient %></li>
 </ul>
 </td>
 </tr>
<% i += 1 %> 

I don't like that I have to define an i variable, is there a better way?

Answer 1

Rails has a built in method, cycle, which will cycle between two more more options for you, so you don't have to manage the "Even"/"Odd" selection.

<% @patients.each do |patient| %>
 <%= content_tag :tr, :class => cycle('Even', 'Odd') do %>
 <%= content_tag :td, link_to(patient.id, patient) %>
 <% [:username, :first_name, :last_name, :email, :active, :disabled].each do |property| %>
 <%= content_tag :td, patient.user.send(property) %>
 <% end %>
 <td>
 <ul class="Horizlist">
 <%= content_tag :li, link_to('Detail', patient) %>
 </ul>
 </td>
 <% end %>
<% end %>

If you happen to use Haml, it looks quite nice. :)

- @patients.each do |patient|
 %tr{:class => cycle('Even', 'Odd')}
 %td= link_to(patient.id, patient)
 - [:username, :first_name, :last_name, :email, :active, :disabled].each do |property|
 %td= patient.user.send(property)
 %td
 %ul.Horizlist
 %li= link_to('Detail', patient)

• sepp2k: Damn, how did I not know that? This is of course better than defining your own helper. +1
• user36: Also, if this is just for styling purposes: you can do that with CSS without classes.

Answer 2

First of all ruby has an each_with_index method, so you can do @patients.each_with_index do |patient, i| instead of keeping a counter manually.

However with the conditional inside the loop that is still too much logic for the view in my opinion. What I'd do is define a helper for this, which might look like this:

# For each item in the given collection, yield that item and embed the
# result in the given tag. The class attribute of that tag alternates
# between class1 and class2
def alternating(collection, tag, class1, class2, html => {})
 collection.each_with_index do |item, i|
 html[:class] = i % 2 == 0 ? class1 : class2
 content_tag(tag, html, false) do
 yield item
 end
 end
end

And then call it like this:

<% alternating(@patients, :tr, 'Even', 'Odd') do |patient| %> 
 <td><%= link_to patient.id, patient %></td>
 <td><%= patient.user.username %></td>
 <td><%= patient.user.first_name %></td>
 <td><%= patient.user.last_name %></td>
 <td><%= patient.user.email %></td>
 <td><%= patient.user.active %></td>
 <td><%= patient.user.disabled %></td>
 <td>
 <ul class="Horizlist">
 <li><%= link_to 'Detail', patient %></li>
 </ul>
 </td>
<% end %>