The benchmark method takes an optional message argument and an optional logging level argument (:debug, :info, :warn, or :error). It records how long the wrapped code takes to run. It requires a block argument, so it usually looks something like:

<% benchmark "It took this long:" do %>
 <%= my_long_method %>
<% end % >

The message and the length of time it takes to run will end up in the logs.

The cache method lets you flag fragments of your view to be kept for caching. Like benchmark, cache wraps around the view code it’s meant to work on with a block argument:

<% cache do %>
  <%= my_repetitive_method_that_should_be_cached %>
<% end % >

You should only cache information that doesn’t change very often, but many HTML components are pretty stable.

The capture method wraps around view code and stores its output to a variable. You can then reference the variable and have that content appear wherever you need. In operation, it looks like a variable assignment to a method:

<% @trapped_content = capture do %>
  <%= content_to_put_in_there %>
<% end % >

Once you’ve captured it, you can reference @trapped_content wherever it is convenient.

The content_for method is much like capture, but instead of putting the content in a variable, it lets you create a named block you can yield to in order to include the content.