hydra_attribute

hydra_attribute is an implementation of EAV (Entity-Attribute-Value) pattern for ActiveRecord models.

Requirements

ruby >= 1.9.2
active_record >= 3.1

Installation

Add the following line to Gemfile: ruby gem 'hydra_attribute' and run bundle install from your shell.

Then we should generate our migration: shell rails generate migration create_hydra_attributes
The content should be: ```ruby
class CreateHydraAttributeTables < ActiveRecord::Migration def up create_hydra_entity :products do |t| # add here all other columns that should be in the entity table t.timestamps end end

def down drop_hydra_entity :products end end ```

or if we have already the entity table

class CreateHydraAttributeTables < ActiveRecord::Migration
  def up
    migrate_to_hydra_entity :products
  end

  def down
    rollback_from_hydra_entity :products
  end
end

Usage

Create model

rails generate model Product type:string name:string --migration=false
rake db:migrate

and add use_hydra_attributes to Product class ruby class Product < ActiveRecord::Base use_hydra_attributes end

Starting from version 0.4.0 use_hydra_attributes method will be removed. ruby class Product < ActiveRecord::Base include HydraAttribute::ActiveRecord end

Create hydra attributes

Product.hydra_attributes.create(name: 'color', backend_type: 'string', default_value: 'green')
Product.hydra_attributes.create(name: 'title', backend_type: 'string')
Product.hydra_attributes.create(name: 'total', backend_type: 'integer', default_value: 1)

Creating method accepts the following options: * name. The required parameter. Allowed any string.
* backend_type. The required parameter. Allowed one of the following strings: string, text, integer, float, boolean and datetime. * default_value. The optional parameter. Allowed any value. By default is nil. * white_list. The optional parameter. Should be true or flase. By defauls is false. if pass white_list: true this attribute will be added to white list and will be allowed for mass-assignment. This parameter is in black list for creation by default so if you want to pass it, you have to pass the role as: :admin too.

    Product.hydra_attributes.create({name: 'title', backend_type: 'string', white_list: true}, as: :admin)

Create records

Product.create
#<Product id: 1, hydra_set_id: nil, created_at: ..., updated_at: ..., color: "green", title: nil, total: 1>
Product.create(color: 'red', title: 'toy')
#<Product id: 2, hydra_set_id: nil, created_at: ..., updated_at: ..., color: "red", title: "toy", total: 1>
Product.create(title: 'book', total: 2)
#<Product id: 3, hydra_set_id: nil, created_at: ..., updated_at: ..., color: "green", title: "book", total: 2>

Add new hydra attribute in runtime

Product.hydra_attributes.create(name: 'price', backend_type: 'float', default_value: 0.0)
Product.create(title: 'car', price: 2.50)
#<Product id: 4, hydra_set_id: nil, created_at: ..., updated_at: ..., color: "green", title: "car", total: 2, price: 2.5>

Create hydra set

Hydra set allows set unique attribute list for each entity.

hydra_set = Product.hydra_sets.create(name: 'Default')
hydra_set.hydra_attributes = Product.hydra_attributes.where(name: %w(color title price))

Product.create(color: 'black', title: 'ipod', price: 49.95, total: 5) do |product|
  product.hydra_set_id = hydra_set.id
end
#<Product id: 5, hydra_set_id: 1, created_at: ..., updated_at: ..., color: "black", title: "ipod", price: 49.95>

Notice: the total attribute was skipped because it doesn't exist in hydra set.

Obtain data

Product.where(color: 'red')
# [#<Product id: 2, hydra_set_id: nil, created_at: ..., updated_at: ..., color: "red", title: "toy", price: 0.0, total: 1>]
Product.where(color: 'green', price: nil)
# [
    #<Product id: 1, hydra_set_id: nil, created_at: ..., updated_at: ..., color: "green", title: nil, price: 0.0, total: 1>,
    #<Product id: 3, hydra_set_id: nil, created_at: ..., updated_at: ..., color: "green", title: "book", price: 0.0, total: 2>
# ]

Notice: the attribute price was added in runtime and records that were created before have not this attribute so they matched this condition where(price: nil)

Order data

Product.order(:color, :title).first
#<Product id: 5, hydra_set_id: 1, created_at: ..., updated_at: ..., color: "black", title: "ipod", price: 49.95>
Product.order(:color, :title).reverse_order.first
#<Product id: 2, hydra_set_id: nil, created_at: ..., updated_at: ..., color: "red", title: "toy", price: 0.0, total: 1>

Select concrete attributes

Product.select([:color, :title])
# [
    #<Product id: 1, hydra_set_id: nil, color: "green", title: nil>,
    #<Product id: 2, hydra_set_id: nil, color: "red", title: "toy">,
    #<Product id: 3, hydra_set_id: nil, color: "green", title: "book">,
    #<Product id: 4, hydra_set_id: nil, color: "green", title: "car">,
    #<Product id: 5, hydra_set_id: 1, color: "black", title: "ipod">
# ]

Notice: id and hydra_set_id attributes are forced added because they are important for correct work.

Group by attribute

Product.group(:color).count
# {"black"=>1, "green"=>3, "red"=>1}

Wiki Docs

Notice

The each new minor version doesn't guarantee back compatibility with previous one until the first major version will be released.

Contributing

Fork it
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Added some feature')
Push to the branch (git push origin my-new-feature)
Create new Pull Request