dynamic_attributes

dynamic_attributes is a gem that lets you dynamically specify attributes on ActiveRecord models, which will be serialized and deserialized to a given text column.

Requirements

Rails 2.x

Installation

config.gem ‘dynamic_attributes’, sudo rake gems:install
gem install dynamic_attributes

Usage

To add dynamic_attributes to an AR model, take the following steps:

Create a migration to add a column to serialize the dynamic attributes to:

class AddDynamicAttributesToDynamicModels < ActiveRecord::Migration
  def self.up
    add_column :dynamic_models, :dynamic_attributes, :text
  end

  def self.down
    remove_column :dynamic_models, :dynamic_attributes
  end
end

Add dynamic_attributes to your AR model:

class DynamicModel < ActiveRecord::Base
  has_dynamic_attributes
end

Now you can add dynamic attributes in several ways. Examples:
- New: DynamicModel.new(:title => ‘Hello’, :field_summary => ‘This is a dynamic attribute’)
- Create: DynamicModel.create(:title => ‘Hello’, :field_summary => ‘This is a dynamic attribute’)
- Update:
  - dynamic_model.update_atribute(:field_summary, ‘This is a dynamic attribute’)
  - dynamic_model.update_atributes(:field_summary => ‘This is a dynamic attribute’, :description => ‘Testing’)
- Set manually: dynamic_model.field_summary = ‘This is a dynamic attribute’

Options

The has_dynamic_attribute call takes three different options:

:dynamic_attribute_field
- Defines the database column to serialize to.
:dynamic_attribute_prefix
- Defines the prefix that a dynamic attribute should have. All attribute assignments that start with this prefix will become dynamic attributes. Note that it’s not recommended to set this prefix to the empty string; as every method call that falls through to method_missing will become a dynamic attribute.
:destroy_dynamic_attribute_for_nil
- When set to true, the module will remove a dynamic attribute when its value is set to nil. Defaults to false, causing the module to store a dynamic attribute even if its value is nil.

By default, the has_dynamic_attributes call without options equals to calling:

has_dynamic_attributes :dynamic_attribute_field => :dynamic_attributes, :dynamic_attribute_prefix => ‘field_’, :destroy_dynamic_attribute_for_nil => false

Take a look at the code Rdoc for more information!

Note on Patches/Pull Requests