resort

Resort provides sorting capabilities to your Rails 3 models.

Install

$ gem install resort

Or in your Gemfile:

gem 'resort'

Rationale

Most other sorting plugins work with an absolute position attribute that sets the weight of a given element within a tree. This field has no semantic sense, since "84" by itself gives you absolutely no information about an element's position or its relations with other elements of the tree.

Resort is implemented like a linked list, rather than relying on absolute position values. This way, every model references a next element, which seems a bit more sensible :)

Usage

You must add two fields (next_id and first) to your model's table:

class AddResortFieldsToProducts < ActiveRecord::Migration
  def self.up
    add_column :products, :next_id, :integer
    add_column :products, :first,   :boolean
  end

  def self.down
    remove_column :products, :next_id
    remove_column :products, :first
  end
end

Then in your Product model:

class Product < ActiveRecord::Base
  resort!
end

NOTE: By default, Resort will treat all products as a single big tree. If you wanted to limit the tree scope, i.e. treating every ProductLine as a separate tree of sortable products, you must override the siblings method:

class Product < ActiveRecord::Base
  resort!

  def siblings
    # Tree contains only products from my own product line
    self.product_line.products
  end
end

API

Every time a product is created, it will be appended after the last element.

Moreover, now a product responds to the following methods:

first? — Returns true if the element is the first of the tree.
append_to(other_element) — Appends the element after another element.

And the class Product has a new scope named ordered that returns the products in order.

Under the hood

Run the test suite by typing:

rake spec

You can also build the documentation with the following command:

rake docs

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 us a pull request. Bonus points for topic branches.