JSON-Stored Fields¶ ↑

Allows for a group of “unimportant” fields to be stored as a JSON hash, rather than as real database columns.

This is useful in cases where you have many classes inheriting from a base class, but with drastically different fields which would clutter up the database.

Obviously this prevents you from searching for these records based upon this data.

However, it does enable you to dynamically add and remove fields from your models at runtime. For example, you can allow the user to specify extra fields for a model, and then get and set them at runtime using json_field_get() and json_field_set().

Installation¶ ↑

ruby script/plugin install git://github.com/aurorasoft/json_fields.git

Usage¶ ↑

Fields are defined using the following syntax :

has_json_field :field1, :field2, :field3

These fields can then be accessed as per usual, but are stored as a JSON hash in the “json_field” column (which you will need to add as a :text field).

Example for migration:
add_column :pages, :json_field, :text

If you don’t like the field named “json_field”, you can change it using :

set_json_field :another_field_here

Then, all data will be stored in the specified field.

Example¶ ↑

An entirely contrived example:

class TestBase < ActiveRecord::Base
end

class SimpleTest < TestBase
  has_json_field :your_name, :your_quest, :your_favourite_colour
end

class ComplexTest < TestBase
  has_json_field :square_root_of_pi, :distance_to_moon_in_meters
end

class ImpossibleTest < TestBase
  has_json_field :air_speed_velocity_of_an_unladen_swallow
end

Runtime-Defined Fields¶ ↑

In cases where you need to dynamically add and use fields at runtime (eg. custom fields) you can also set and get arbitrary fields using:

json_field_get(:field_name, 'foo') # => "foo"
json_field_get(:field_name)        # => "foo"

Caveats¶ ↑

• Internally we use .to_json, which means that symbols will be converted to strings. As such, you may need to take care.

• Any Rails code handling whether the instance has changed will likely not report changes to the JSON fields.

Licensing¶ ↑

Copyright © 2008-2009 Aurora Software (www.aurorasoft.com.au), released under the MIT license