PreferenceFu
============

This plugin, greatly inspired by Jim Morris' blog post 
(http://blog.wolfman.com/articles/2007/08/07/bit-vector-preferences), aims to make it easy and flexible to store boolean 
preferences for an ActiveRecord model. This can be also used as a very quick way to setup an ACL.

Because the values are stored within a bit vector, a virtually unlimited number of preferences can be created without 
additional  migrations.

Feel free to email me with any suggestions or problems.

Blog: http://www.brennandunn.com
Email address: me@brennandunn.com


Setup
=====

Simply add an integer column to each table of the database that requires preferences. By default, the column used is 
'preferences', but by defining a method called preferences_column this can be modified.

  def preferences_column
    'other_column'
  end

Your migration should probably look something like this:
  
  add_column :people, :preferences, :integer
    

Examples
========

Using PreferenceFu is very simple.

  class User < ActiveRecord::Base
  
    has_preferences :send_email, :change_theme, :delete_user, :create_user
    
    set_default_preference :send_email, true
  
  end
  
For new AR objects, all preference options will be set to false. This can be overwritten using set_default_preference. I 
really recommend you read the 'Warning' section below.

Setting a key:
  ...individually
  @user.prefs[:delete_user] = true 
    
  ...mass assignment (useful with the params hash)
  @user.prefs = {:delete_user => true, :create_user => true}
  
Setting an option as true doesn't necessarily need to be done with the Boolean true - in fact, the Fixnum 1, and strings 
'1', 'y' and 'yes' are all valid. This is particularly helpful for checkbox form posts.

   @user.prefs[:create_user] = 'yes'


Fetching a key:
  @user.prefs[:change_theme]  => false
  

Getting the index of a key:
  @user.prefs.index(:delete_user)  => 4
  

Enumerable...
  @user.prefs.size  => 4
  
  @user.prefs.each do |key, value|
    puts "#{key} is set to #{value}"
  end
  

Warning
=======

This works by taking the index of the splat supplied in has_preferences as the power of two, summing all values, and 
storing the sum in the preferences column. Because of this, the first item in the splat will be identified by 1, the 
second by 2, the third by 4, etc. Once you start using PreferenceFu in production, add new options to the *end* of the 
splat. At the moment, there's no safe way to delete a preference item at the moment. Any advice is welcome! 

  

Copyright (c) 2008 Brennan Dunn, released under the MIT license