has_flags.rb - Has Bit Flags Plugin

Overview

The has_flags plugin provides a simple way to define and access multiple boolean flags that map to a single integer database column. The primary objects for using flags are:

1) control and access the state of an object
2) to enable finding database rows with a particular state
3) to ease long term maintenance by providing a database definition independent way of extending states
4) to be able to adapt to legacy systems that use this approach

Conventions:

*) Db Column Name: bit_flags
*) attribute writer (setter) accepts true, 'true', 'yes', :yes, 1, '1', 'ok' to evaluate true.  all others are false.

Sample Use:

class PayableInvoice << ActiveRecord::Base
  has_flags [ :active, true, :ok_to_post, 7, :posted, :archived ]
end

instance attrs

invoice = Payable.new => new payable object created, uses 'after_initialize' to set defaults
invoice.active?      => true
invoice.active       => true
invoice.ok_to_post?  => false
invoice.bit_flags    => 1  # follows the 'active=true' configuration

invoice.active = v   => true where v is in [ true, 'true', 1, '1', 'yes', 'YeS', :yes, :ok 'OK', "oK" ]
invoice.active = v   => false where v.to_s.upcase is not in the list above

Class Methods

PayableInvoice.flags    => { "active"=>1, "ok_to_post"=>128, "posted"=>256, "archived"=>512 }
PayableInvoice.mask(:ok_to_post, :posted) => 384 (0b0110000000)
PayableInvoice.mask(:active, :archived)   => 512 (0x1000000000)

Finders

PayableInvoice.find_by_flags(:active, :ok_to_post)  => returns a list of objects that are 'active' and 'ok to post'
PayableInvoice.find_by_flags(:not_active)           => returns a list of objects that are not active

For other examples, see RainCityOnRails.com/has_flags