Dynattribs (Dynamic Attributes)

Dynattribs makes it easy to declare dynamic attributes in ActiveRecord classes.

Overview

The Dynattribs Gem (Dyanmic Attributes) provide a database backed attributes to ActiveRecord::Base classes, without having to declare table columns for each attribute. A bit of NoSQL data flexibility for traditional database backed ActiveRecord classes.

The dynamic attributes are stored as a JSON encoded Hash, and can be persisted into any field that can store text data.

Installation

You can use the Dynattribs in your Rails project by including the following in your Gemfile:

gem 'dynattribs'

Usage

To use Dynattribs you need to include the mixin in your class definition, preferably at the top.

To define the names of the dynamic attributes use the “dynamic_attr_accessor” method. This method takes two of more arguments. The first argument is the name of the database field that the dynamic attributes will be persisted to. The other arguments are the names of the dynamic attributes. It is meant to be used in a similar way to the familure “attr_accessor” method

Example

The following example defines a dynamic “info” field for the MyClass class, with the new info field’s data being persisted to the “extra_data” database field.

class MyClass < < ActiveRecord::Base
  include Dynattribs

  dynamic_attr_accessor :extra_data, :info
end

Database

The dynamic attributes are stored converted to a JSON encoded string before storing to the nominated database field. Therefore, you will need to add a string column to the table of any class you wish to add dynamic attributes too.

A String field would work, but a “text” field would be best due to the large amount of data that could be stored in the dynamic attributes.

To add the new column, create a migration, e.g.

rails g migration add_model_dynamic_attribute

And modify the migration to look something like this:

class AddModelDynamicAttribute < ActiveRecord::Migration
  def change
    add_column :models, :dynamic_attribs, :text
  end
end

In The Wild

Dynattribs is used in a number of production systems:

Capstory - Private Group Photo Albums

Authic - A Local shopping Sales Notification Service

If you are using Dynattribs in your project and would like to be added to this list, please get in touch!

Contributing

Contributions are very welcome. Please ensure all pull requests include suitable test coverage and all tests are passing.

Authors

• James McGrath

Licence

This code is licensed under the MIT license. See MIT-LICENCE for more details.