Resort - positionless sorting for your Rails 3 models
Lately we have been working on some drag & drop interfaces for some client work that needed model sorting. As you might know, on the front-end layer there are plenty of solutions for that (being jQuery draggable/sortable a really good one). But what to use on a model level?
We first thought of some acts_as_list
-ish kind of plugins, and after thoroughly reviewing them all, we came up with an observation.
Most of 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. After you just read this, just like us, you won't be able to sleep. Think about it. All these arbitrary numbers in your database columns. Flowers aren't pretty anymore. Life sucks.
Does it?
Of course it doesn't! Computer science brings us beautiful data structures to satiate our need for beauty. Look at the structure of a linked list for example, and you will think: enough :order => "position"
already! We don't need an arbitrary position
field. We just need every model to reference a next
and a previous
. Yeah, it smells like those old C tutorials, but it's worth it :)
So, unlike most Rails sorting plugins (acts_as_list, etc), Resort is based on linked lists rather than absolute position fields.
TL;DR - How can I use it?
$ gem install resort
Or in your Gemfile:
gem 'resort'
As you just learned, you must add two fields (next_id
and first
) to your model's table, let's say, Product
:
# db/migrate/283792358_add_resort_fields_to_products.rb
class AddResortFieldsToProducts < ActiveRecord::Migration
def self.up
add_column :products, :next_id, :integer
add_column :products, :first, :boolean
add_index :products, :next_id
add_index :products, :first
end
def self.down
remove_column :products, :next_id
remove_column :products, :first
end
end
Then in your Product
model:
# app/models/product.rb
class Product < ActiveRecord::Base
resort!
end
By default, Resort will treat all products as a single big tree. But what if you have different ProductLines
, and want to sort products separately withi each product line? As a sortable product, you have to tell Resort who you siblings are. To do that, just override the siblings
method:
# app/models/product.rb
class Product < ActiveRecord::Base
resort!
def siblings
# Tree contains only products from my own product line
self.product_line.products
end
end
Now your products are enhanced with two methods doing the following:
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 th products in order. Easy huh?
Learn more
To learn more, you can check out the documentation. Also, if you want to get involved, just check out the [source code at Github](http://github.com/codegram/resort and start hacking on it! :)
UPDATE: We did some benchmarks comparing the performance of Resort against RankedModel and ActsAsList.