While it’s fairly easy to redefine where the attachments get saved on a per-model basis with the :url and :path options, I very much prefer to do something once and then never have to think about it again.  (This preference is part of the reason that this is only my second post on a blog I’ve had since December.)  Thankfully, overriding the defaults for your entire app is easy.  Just make a file called paperclip_defaults.rb in your config/initializers directory and fill it with the following lovely code:

module Paperclip
  class Attachment
    def self.default_options
      @default_options ||= {
        :url           => "/system/:class/:attachment/:id/:style/:basename.:extension",
        :path          => ":rails_root/public/system/:class/:attachment/:id/:style/:basename.:extension",
        :styles        => {},
        :default_url   => "/:attachment/:style/missing.png",
        :default_style =>  riginal,
        :validations   => [],
        :storage       => :filesystem
      }
    end
  end
end

Just change the options in that block to suit your fancy, and the changes will take place across your entire application.

Recently I ran into an issue where I needed to run conditions on an associated table in just such a search and I managed to find what seems to be an undocumented (or under-documented at least) feature of ActiveRecord. For the sake of using the same example as every other Rails tutorial out there, let’s assume that I’m running a search on Authors, and that an Author has_many books. All we have to do is make a hash within the conditions hash with the name of the associated table. Searching both tables is easy as:

Author.find(:conditions => {:first_name => params[:first_name], :last_name => params[:last_name], :books => { :title => params[:book_name] } }, :include => :books)

If we were writing this as an advanced search and wanted the parameters to be optional, we would break it out like this:

conditions = {}
conditions[:first_name] = params[:first_name] unless params[:first_name].blank?
conditions[:last_name] = params[:last_name] unless params[:last_name].blank?
conditions[:books] = {:title => params[:book_name]} unless params[:book_name].blank?

@authors = Author.find(:conditions => conditions, :include => :books)

Simple!