Allows the use of Rails fragment caching helpers from within mailers.

Tested in Rails 3.2, 4.0, 4.1 and 4.2. If you're using Rails 5 then you don't need this gem as this feature has now been added to Rails 5.

Add this line to your application's Gemfile:

gem 'mailer_fragment_caching'

And then execute:

$ bundle

Make sure you have caching enabled in your environment configuration:

config.action_controller.perform_caching = true

And configure your cache store as your please:

config.cache_store = :mem_cache_store

Include the module within your mailer file.

class CoolMailer < ActionMailer::Base

  include MailerFragmentCaching

  def cool_email
    ...
  end

end

Use cached fragments in your mailer templates, just like regular views.

<% cache @thing do %>
  <%= render @thing %>
<% end %>