Y’day I noticed that action caching stopped working when I moved the caching mechanism from ‘file storage’ to ‘memcached’. After some investigation I found that cache_fu is broken.

Here is the code from ActionController.rb .

 
def caches_action(*actions)
  return unless cache_configured?
  options = actions.extract_options!
  filter_options = { :only => actions, :if => options.delete(:if), :unless => options.delete(:unless) }

  cache_filter = ActionCacheFilter.new(:layout => options.delete(:layout), 
                                       :cache_path => options.delete(:cache_path), 
                                       :store_options => options)
  around_filter(cache_filter, filter_options)
end

class ActionCacheFilter #:nodoc:
  def initialize(options, &block)
    @options = options
  end

  ...
end

Notice that when an instance of ActionCacheFilter is created, the list of actions on which caching is to be performed is not passed. cache_fu assumes that it has access to *actions and that’s why the code fails.

Here is snippet from cache_fu .

 
def self.setup_rails_for_action_cache_options
  puts 'setup_rails_for_action_cache_options called'
  ::ActionController::Caching::Actions::ActionCacheFilter.class_eval do
    # convert all actions into a hash keyed by action named, with a value of a ttl hash (to match other cache APIs)
    def initialize(*actions, &block)
      puts 'initialize in action is called'
      if [].respond_to?(:extract_options!)
        #edge
        puts "actions is #{actions.inspect}" 
        @options = actions.extract_options!
        @actions = actions.inject(@options.except(:cache_path)) do |hsh, action|
            action.is_a?(Hash) ? hsh.merge(action) : hsh.merge(action => { :ttl => nil })
          end
      ...
    end
  end
end

As you can see in the intialize method of ‘ActionCacheFilter’ class the first parameter is erroneously named ‘actions’. It should be more like options.

The fix is easy . We need to do three things which are at line numbers 20,33 and 55.