Working With Rails

Has Flags

= has_flags.rb – Has Bit Flags Plugin

Copyright 2006, Rain City Software, Inc. License: Apache 2.0, Version 0.1.4 11-Aug-2006

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 http://RainCityOnRails.com/has_flags

NOTE: This description has been extracted from the Plugin README and so the formatting may need updating to make browser friendly