An ActiveRecord emulating Tableless model which works with Rails 3.1

tableless.rb

class Tableless < ActiveRecord::Base

  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

  def self.columns()
    @columns ||= [];
  end

  def self.columns_hash
    h = {}
    for c in self.columns
      h[c.name] = c
    end
    return h
  end

  def self.column_defaults
    Hash[self.columns.map{ |col|
      [col.name, col.default]
    }]
  end
    
  def self.descends_from_active_record?
    return true
  end
      
  def persisted?
    return false
  end
      
  # override the save method to prevent exceptions
  def save( validate = true )
    validate ? valid? : true
  end
     
end

@matpowel: Many thanks for taking the time to help! I'm suspecting that my problem has to do with not instantiating the model? My plan is to add to this "fake" table at boot, using values from a configuration file...

I should add that with the example above I get "No such table: 'stuffs'" and not "tablelesses".

This all works for me.. note I removed your initialize method as it's superfluous, that's what the default one will do but without the unsafe eval.

class Thing < Tableless
  belongs_to :stuff_thing

  column :stuff_thing_id, :integer
  column :name, :string
end

class StuffThing < Tableless
  belongs_to :stuff
  has_many :things

  column :stuff_id, :integer
end

class Stuff < Tableless
  has_many :stuff_things
  has_many :things, :through => :stuff_things

  column :id, :integer
  column :name, :string
  column :value, :string
end

And then you can use them as normal, except that ARel won't chain the has many through very well, I don't know whether your stuff_things etc are actually real AR models, if they are it will work normally.

1.8.7 :064 >   s = Stuff.new( :id => 10, :name => "foo", :value => "bar" )
WARNING: Can't mass-assign protected attributes: id
 => #<Stuff id: nil, name: "foo", value: "bar"> 
1.8.7 :065 > s.stuff_things << StuffThing.new( :stuff => s )
 => [#<StuffThing stuff_id: nil>] 
1.8.7 :067 > s.stuff_things.length
 => 1
s.things << Thing.new( :name => "wild thing" )
 => [#<Thing stuff_thing_id: nil, name: "wild thing">]

Thanks for this gist, I made this demo with it: https://github.com/stevemartin/tableless_form