Firstly, apologies for not updating regularly enough (last post was in September – yikes!). We have been busy working on two freelance projects since then: firstly with South East Forum for 55 Degrees; and finally with HiredHelp, which is a service provider listing page for Hermes Technologies based in Ireland.

I want to start off the new series of posts with interesting tidits I learnt while developing on these two projects.

On the HiredHelp website, we try to cache as much of the DB calls as possible using memecached with the cache_fu plugin. One of the obstacles we came across was if we had to cache the index action of say a list of babysitters with pagination added in, the subsequent paginated pages do not show. This is due to the fact that the cache is storing the page as ‘babysitters/index’ and not ‘babysitters?page=xxx’.

You will need to provide a ‘cached_path’ to the caches_action in the controller.

For example:

This is the ‘caches_action’ method within the controller:

  
      caches_action :index, :cache_path => :index_cache_path.to_proc
      

      def index
        @babysitters = Babysitter.cached(:list).paginate(:page => params[:page],:per_page => 10)
      end
   

  private
        def index_cache_path
          p = ''
          p = params[:page] if params[:page] and params[:page] != 1
          'babysitters/' + p
    end
   

The ‘cached’ method was provided by cache_fu and calls the method ‘list’ within the Babysitter model. The index_cache_path method simply appends the page params from the wii_paginate plugin to the end of the index url. So pages like ‘babysitters?page=2′ will be cached as ‘babysitters/2′ etc.

Now to expire the paginated pages, I wrote a custom method within my sweepers file:

  
  #within BabysitterSweeper
  

  def expire_cache
    total = (Babysitter.list.size.to_i)
    if total <= 10
      expire_fragment("babysitters/index")
    else
      pages = (total % 10) + (total /10) -1
      1.upto(pages) do |page|
        expire_fragment("babysitters/#{page}")
      end
      expire_fragment("babysitters/index")
      

    end
  end
  

The method computes the number of listings allowed per page as stipulated in the wii_paginate call in the index action. In our case it is 10. If the number of entries is less than 10, that means we only expire the index action. If not, we calculate the number of paginated pages there are. If we have say 22 entries that will be split into 3 paginated pages with 2 pages containing 10 entries and a third page with 2 entries. The ‘expire_cache’ method will expire the fragements labelled ‘babysitters/2′ etc from the index call such as ‘babysitters?page=2′.