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    <p>Here's how I'd implement the metaprogramming part that creates the accessor methods and sets them as attr_accessibles.</p> <p>I'm using YAML intead of XML just as a personal crusade. I even went ahead and implemented the unneeded serialization part just to nudge you towards YAML.</p> <pre><code>require 'yaml' require 'rubygems' require 'active_support' require 'active_record' module Yamlable def self.included m m.extend ClassMethods end module ClassMethods def add_yaml_fields *args write_inheritable_array(:yaml_fields, args) attr_accessor(*args) attr_accessible(*args) before_save :serialize_yaml_fields end end def serialize_yaml_fields self.yamlable_column = read_inheritable_attribute(:yaml_fields)\ .inject({}) { |h, a| h[a] = send(a); h }.to_yaml end def initialize(*args) super YAML::load(yamlable_column).each { |k, v| send("#{k}=", v) } end end class ParentModel &lt; ActiveRecord::Base include Yamlable add_yaml_fields :foo, :bar end class ChildModel &lt; ParentModel end # look, they're there: y ChildModel.read_inheritable_attribute(:yaml_fields) </code></pre> <p>Now, if you want to know why your particular code didn't work, you'll have to post more of it.</p> <hr> <p>I should probably expand a bit on class inheritable attributes. They are a bit like class variables, a bit like class instance variables.</p> <p>If you define an inheritable attribute in a class, all its subclasses will share it. But if you update said attribute in a child class, this child class copies the original attribute and updates it, so the updates are exclusive to it and don't affect other classes around it in the inheritance chain.</p> <p>With the normal <code>write_inheritable_attribute</code> method, setting it on a child class will simply override the value from the parent. With inheritable arrays and hashes, <code>write_inheritable_*</code> will concat / merge to the parent class's values. </p> <hr> <p>So, in practice, my <code>add_yaml_fields</code> works like this:</p> <pre><code>class Parent add_yaml_attributes :foo class Child1 &lt; Parent add_yaml_attributes :bar class Child2 &lt; Parent add_yaml_attributes :baz </code></pre> <p>With that, the yaml attributes for each class will be:</p> <ul> <li>Parent: foo</li> <li>Child1: foo, bar</li> <li>Child2: foo, baz</li> </ul>
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    1. POHow do you call attr_accessible dynamically in Rails?
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    1. POHow do you call attr_accessible dynamically in Rails?
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    1. COThis seems to be on the right track, but I'm not sure how to integrate this into my parent class, and your example calls "add_yaml_fields" from the parent and not the child. Thanks for any extra advice.
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    2. COthe Yamlable model can be included in any class, and it'll provide add_yaml_fields to it and all its descendants. So, to call it on the ChildModel, just call it there instead of in the parent. No tricks required.
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    3. COThanks so much for trying again! I got it working after changing the "yamlable_column" to "content" which is specific to my DB table. Nice work, I have awarded you the correct answer (and there was so much competition!) Cheers mate.
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