Simple Rails caching library

simple_cache.rb

# A simple expiring cache suitable for use with the :file_store cache store.
# Not particularly threadsafe, and can duplicate work if there are multiple 
# requests for stale data at the same time.
#
# Usage:
#   SimpleCache.fetch('my_data', 15.minutes) do
#     MyModel.expensive_query
#   end
#
# Make sure to set up the cache to use :file store in your environment.rb, 
# like this:
#   config.cache_store = :file_store, "#{RAILS_ROOT}/tmp/cache"
module SimpleCache
  # Choose a cache_key and expiration time (e.g. 15.minutes), and pass a
  # block that returns the data you want to cache. The block will only be
  # evaluated if the cache has expired.
  def self.fetch(cache_key, expires_in)
    data = Rails.cache.read(cache_key)
    if !data || data[:inserted_at] <  expires_in.ago.utc
      value = yield
      Rails.cache.write(cache_key, {
        :inserted_at => Time.now.utc,
        :data => value
      })
      return value
    else
      return data[:data]
    end
  end
end