Rails model - next and previous objects

Its been a long time since, I posted anything. So, I thought I will let something go.

In one of my Rails application, while showing an object I need to show links to the previous and next objects. I think, this is a common task in many Rails application, the way I am doing it is I have extended the Active Record Base class so that all my models have this function. There are numerous way to include this, choose one which you think most suits your purpose or which you like.

module ActiveRecord #:nodoc:
  class Base
    def next_id
      @next ||= self.class.find(:first,:select => ['id'],:conditions => ['id > ?', id], :order => 'id')
      @next ? @next.id : nil
    end

    def previous_id
      @previous ||= self.class.find(:first,:select => ['id'],:conditions => ['id < ?', id], :order => "id desc")
      @previous ? @previous.id : nil
    end
  end
end

Let this file be called 'base_ext.rb' and put it in 'lib' folder of your application.

Now, in your model files add the line

require 'base_ext'

at the top this will ensure that this file is loaded before your model class is declared.

Now, in your views you can use something like this:

  <%= link_to '« Previous',{:id => @creation.previous_id},:class => "alignleft" if @creation.previous_id %>
  <%= link_to 'Next »',{:id => @creation.next_id},:class => "alignright" if @creation.next_id %>