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Gem Version

Allows the addition of custom "magic" columns and attributes on a per-model or per-parent-model basis. This is useful for situations where custom fields are required for a specific model or for multi-user, multi-account environments where accounts can customize attributes for subordinate models.

NOTE: This plugin is probably not production-ready. While all the described features work, not all features have been tested. It was originally a Rails 2 plugin written by Brandon Keene and has been updated to a gem with Rails 3 support.


Add to your Gemfile:

gem "has_magic_columns"

Create the migrations for MagicColumns and migrate:

rails g has_magic_columns:install
rake db:migrate



Sprinkle a little magic into an existing model:

class Person < ActiveRecord::Base

Add magic columns to your model:

@charlie = Person.create(:email => "")
@charlie.magic_columns.create(:name => "first_name")

Supply additional options if you have more specific requirements for your columns:

@charlie.magic_columns.create(:name => "last_name", :is_required => true)
@charlie.magic_columns.create(:name => "birthday", :datatype => :date)
@charlie.magic_columns.create(:name => "salary", :default => "40000", :pretty_name => "Yearly Salary")

The :datatype option supports: :check_box_boolean, :date, :datetime, :integer

Use your new columns just like you would with any other ActiveRecord attribute:

@charlie.first_name = "Charlie"
@charlie.last_name = "Magic!"
@charlie.birthday =

Find @charlie and inspect him:

@charlie = User.find(
@charlie.first_name	#=> "Charlie"
@charlie.last_name	#=> "Magic!"
@charlie.birthday	#=> #<Date: 4908497/2,0,2299161>
@charlie.salary     #=> "40000", this is from :salary having a :default

Inherited Model

A child can inherit magic columns from a parent. To do this, declare the parent as having magic columns:

class Account < ActiveRecord::Base
  has_many :users
@account = Account.create(:name => "BobCorp")

And declare the child as having magic columns :through the parent.

class User < ActiveRecord::Base
  belongs_to :account
  has_magic_columns :through => :account
@alice = User.create(:name => "alice", :account => @account)

To see all the magic columns available for a child from its parent:

@alice.magic_columns #=> [#<MagicColumn>,...]
@account.magic_columns #=> [#<MagicColumn>,...]
@alice.account.magic_columns #=> [#<MagicColumn>,...]

To add magic columns, go through the parent or child:


All children for a given parent will have access to the same magic columns:

@alice.magic_columns.create(:name => "salary")
@alice.salary = "40000"

@bob = User.create(:name => "bob", :account => @account)
# Magic! No need to add the column again!
@bob.salary = "50000"

To Do

Here's a short list of things that need to be done to polish up this gem:

  • Test other parts of the data model (e.g. magic_attributes, magic_options)
  • Benchmark and optimize



See the CONTRIBUTORS guide.


  • Thank you to Brandon Keene for his original work making this plugin.
  • Thank you to the will_paginate gem for iinspiration and code examples for how to test a Rails plugin.