acts_as_ordered¶ ↑

Author

Thomas Kadauke - tkadauke (at) imedo.de

Copyright

Copyright © 2008 imedo GmbH

Licence

MIT

Git

github.com/imedo/acts_as_ordered

Bugs

No dedicated bug tracker yet - Email us or just send pull requests

Find the logical next or previous item of a result set with a simple query.

Dependencies¶ ↑

• Rails 2.0.2 (might also work with 2.1)

Additionaly for testing:

• dry_plugin_test_helper - github.com/imedo/dry_plugin_test_helper

• sqlite3 - www.sqlite.org/

Installation¶ ↑

The easiest way to install this plugin is directly from github:

$ cd vendor/plugins
$ git clone git://github.com/imedo/acts_as_ordered.git

Usage¶ ↑

In your model, simply call acts_as_ordered without any parameters:

class Picture < ActiveRecord::Base
  acts_as_ordered
end

After that, you can access the logical next and previous element in a database result set that is specified by the :conditions and :order parameters.

For example, if Picture p belongs to User u, you can get the next picture belonging to u by calling

p.find_next(:conditions => ['user_id = ?', u.id])

Alternatively, you can use the :source parameter:

Picture.find(:next, :source => p, :conditions => ['user_id = ?', u.id])

Note that you need to give the user id explicitly; the p variable does not store the context of the result set in which you want to find the logical next and previous items.

ActiveRecord’s :order parameter is of course taken into account:

p.find_next(:conditions => ['user_id = ?', u.id], :order => 'created_at ASC')
# equals
p.find_prev(:conditions => ['user_id = ?', u.id], :order => 'created_at DESC')

You can even use multiple order columns, with different sort directions. If you don’t specify any order, a default of ‘id ASC’ is assumed.

The next or previous item is found efficiently: The generated SQL ensures that only one item gets returned from the database.