tableless.rb

class Tableless
  include ActiveModel::Validations
  include ActiveModel::Conversion
  extend ActiveModel::Naming

  attr_accessor :new_record

  def initialize(attributes={})
   self.new_record = attributes.blank?
   attributes && attributes.each do |name, value|
     send("#{name}=", value) if respond_to? name.to_sym
   end
  end

  def new_record?
    return self.new_record
  end

  def persisted?
    false
  end

  def self.inspect
    if self.respond_to?(:attributes)
      "#<#{self.to_s} #{self.attributes.collect{ |e| ":#{ e }" }.join(', ')}>"
    else
      "#<#{self.to_s}>"
    end
  end
end

#rspec

include ActiveModel::Lint::Tests

describe Tableless do
  describe "#initialize" do
    before do
      class Person < Tableless
        attr_accessor :name
      end
    end

    it "takes an array of attributes and sets them" do
      person = Person.new(name: "Sam")
      person.name.should == "Sam"
    end

    it "does not set undefined attributes" do
      person = Person.new(name: "Sam", title: "Prof")
      expect { person.title }.to raise_error(NoMethodError)
    end
  end

  describe "#new_record?" do
    it "should return true for a new object" do
      tableless = Tableless.new
      tableless.new_record?.should == true
    end

    it "should return false for an object with attributes set" do
      tableless = Tableless.new(name: "Sam")
      tableless.new_record?.should == false
    end
  end

  describe "#persisted?" do
    it "should not be persisted" do
      tableless = Tableless.new
      tableless.persisted?.should be_false
    end
  end
end