ConstantizeAttribute
====================

A simple Rails plugin that gives ActiveRecord a macro-style class method for
declaring that certain attributes should have their values serialized with to_s
and deserialized with constantize. This allows you to use Class and Module
objects as attribute values.

Since it uses to_s, the value will be stored as an easily read, easily updated
string in the database, which is often preferable to the YAML you get with
Rails' built in serialize macro.

Note this also works with any other constant object that follows the same
contract with respect to to_s and constantize being symmetrical, for example
an enumeration created with [shameless plug!] the renum gem.

Example
=======

# ... your migration ...
create_table :robots do |t|
  t.column :behavior_module, :string
end

# ... your model ...
class Robot < ActiveRecord::Base
  constantize_attribute :behavior_module
end

# ... some classes or modules you want to store as attribute values ...
module RobotBehaviors
  module Handy
    def self.encounter
      "Is there anything I can help you with?"
    end
  end

  module Evil
    def self.encounter
      "I will destroy all humans."
    end
  end
end

# ... so now,
robby = Robot.create :behavior_module => RobotBehaviors::Evil

# Now "RobotBehaviors::Evil" is in the behavior_module column.

robby.behavior_module.encounter # => "I will destroy all humans."

robby.update_attribute :behavior_module, RobotBehaviors::Handy

# Now "RobotBehaviors::Handy" is in the behavior_module column.

robby = Robot.find :first

robby.behavior_module.encounter # => "Is there anything I can help you with?"

Usage
=====

You can specify multiple attribute names in one call. The constantize_attribute
method is aliased to constantize_attributes if you find that reads better.

Note this will not work with anonymous classes or modules: The definition is
not stored in the database, only the name.


Copyright (c) 2008 John D. Hume, released under the MIT license