Rails model without database

There is a better way to do this in Rails 3: http://railscasts.com/episodes/219-active-model

This is an approach I have used in the past:

In app/models/tableless.rb

class Tableless < ActiveRecord::Base
  def self.columns
    @columns ||= [];
  end

  def self.column(name, sql_type = nil, default = nil, null = true)
    columns << ActiveRecord::ConnectionAdapters::Column.new(name.to_s, default,
      sql_type.to_s, null)
  end

  # Override the save method to prevent exceptions.
  def save(validate = true)
    validate ? valid? : true
  end
end

In app/models/foo.rb

class Foo < Tableless
  column :bar, :string  
  validates_presence_of :bar
end

In script/console

Loading development environment (Rails 2.2.2)
>> foo = Foo.new
=> #<Foo bar: nil>
>> foo.valid?
=> false
>> foo.errors
=> #<ActiveRecord::Errors:0x235b270 @errors={"bar"=>["can't be blank"]}, @base=#<Foo bar: nil>>

There is easier way now:

class Model
  include ActiveModel::Model

  attr_accessor :var

  validates :var, presence: true
end

ActiveModel::Model code:

module ActiveModel
  module Model
    def self.included(base)
      base.class_eval do
        extend  ActiveModel::Naming
        extend  ActiveModel::Translation
        include ActiveModel::Validations
        include ActiveModel::Conversion
      end
    end

    def initialize(params={})
      params.each do |attr, value|
        self.public_send("#{attr}=", value)
      end if params
    end

    def persisted?
      false
    end
  end
end

http://api.rubyonrails.org/classes/ActiveModel/Model.html

I think the blog post you are linking is the best way to go. I would only suggest moving the stubbed out methods into a module not to pollute your code.