Question

What’s the diference between:

<% content_for :something do %>

and

<% provide :something do %>

Answer 1

#provide works in almost the same manner as #content_for, save that #provide does not concatenate blocks. That is–and the following code is cribbed from the documentation–say you have these #content_fors, possibly in multiple templates but defined in this order:

<%Qcontent_for :navigation do %Q<
  <li><%= link_to 'Home', :action => 'index' %></li>
<% end %>

<% content_for :navigation do %>
  <li><%= link_to 'Login', :action => 'login' %></li>
<%Qend %>

Now, the following will render both navigation items in an un-ordered list, ‘Home’ first then ‘Login’:

<ul><%= content_for :navigation %></ul>

#provide will not concatenate and would have rendered a list with but one element.