ActsAsOrderable

Install

gem install acts_as_orderable

and in your Gemfile:

gem 'acts_as_orderable'

Model declaration:

class CoolClass < ActiveRecord::Base
    acts_as_orderable
end

About

Simple Rails gem allowing ActiveRecord models to have order and to move them up and down

Requirements

table.integer :element_order, :default => 0, :null => false

It works well with acts_ac_tree (each node has its own order so they don't interfere with each other)

Use :position => :first or :position => :last to set default new element behavior - should it be append as and first or last element. Default is :last. This default behavior will also be used when switching parents when you use acts_as_tree.

Example

class CoolClass < ActiveRecord::Base
    acts_as_orderable
end

# Creating some records record
a = CoolClass.new(:name => A); a.save
b = CoolClass.new(:name => B); b.save
c = CoolClass.new(:name => C); c.save
d = CoolClass.new(:name => D); d.save

#Order:
0 => A
1 => B
2 => C
3 => D

Lets take element C and lest move it 1 element up

c.move_up(1)

#New Order:
0 => A
1 => C
2 => B
3 => D

Now lest move C 2 elements down

c.move_down(2)

# Order:
0 => A
1 => B
2 => D
3 => C

Additional notes

With acts_as_tree plugin, you use it in the same way, just remember that you operate on a node order.

There is one more thing: if you look into element_order column, numbers are not always like: 0, 1, 2, 3, 4, etc. They are more like 0, 1, 23, 452, 523. That's because when you delete a row, there will be deleted also one "order". But don't worry, everything works fine even then.

Note on Patches/Pull Requests

Fork the project.
Make your feature addition or bug fix.
Add tests for it. This is important so I don't break it in a future version unintentionally.
Commit, do not mess with Rakefile, version, or history. (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull)
Send me a pull request. Bonus points for topic branches.