has_magic_columns

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.

Installation

Add to your Gemfile:

gem "has_magic_columns"

Create the migrations for MagicColumns and migrate:

rails g has_magic_columns:install
rake db:migrate

Usage

Model

Sprinkle a little magic into an existing model:

class Person < ActiveRecord::Base
  has_magic_columns
end

Add magic columns to your model:

@charlie = Person.create(:email => "charlie@example.com")
@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 = Date.today
@charlie.save

Find @charlie and inspect him:

@charlie = User.find(@charlie.id)
@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
  has_magic_columns
end
@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
end
@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:

@alice.magic_columns.create(...)
@account.magic_columns.create(...)

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

Maintainers

Drew Ulmer (latortuga)
Nicholas Zielinski (zieski)

Contribute

See the CONTRIBUTORS guide.

Credits

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.

frederico / has_magic_columns