Partials should have an easier time delegating to other partials.

[andrewculver]

Given a app/views/account/shared/menu/_item.html.erb like so:

<% yield p = np %>

<% method ||= nil %>
<% active ||= nil %>

<%= render "themes/light/menu/item", label: label, method: active do |dp| %>
  <% dp.content_for :icon, p.content_for :icon %>
<% end %>

Note the repetition of content_for for and :icon on that one line. Also, this is only for one named content area. If there were more, the duplication would be even worse. To DRY-up the latter problem, I would probably:

<% [:icon, ...].each do |name| %>
  <% dp.content_for :icon, p.content_for :icon %>
<% end %>

But this is still both ugly as sin and not obvious to someone reading the code what is happening. For example, it's easy to miss that there is a p view context and a dp view context (short for "delegate partial").

I think some good alternatives to this would be something like one of the following:

1. <% p.delegate_to dp %>
2. <% dp.delegate_from p %>

With the final result looking something like this:

<% yield p = np %>

<% method ||= nil %>
<% active ||= nil %>

<%= render "themes/light/menu/item", label: label, method: active do |dp| %>
  <% d.delegate_to dp %>
<% end %>