A Ruby Object that Works Like Javascript's Objects. The idea is to make creating/validating non-model based forms easier.

AssociativeObject.rb

class AssociativeObject
  def eigenclass; class << self; self; end; end

  #form_for requires these methods
  attr_accessor :id
  attr_accessor :errors
  def new_record?; return true; end
  def to_param; return nil; end #for AR object to_param returns nil for new objects
  def to_key; id ? [id] : nil end #borrowed from rails source for dummy object
  def self.model_name;  ActiveModel::Name.new(self); end #how AR determines the name for the params hash.  TODO: allow dynamic assignment

  def initialize hash={}
    return  unless hash #incase nil is passed
    hash.each do |name, value|
      add_association name, value
    end
  end

  def []= key, value
    add_association key, value
  end

  def [] key
    respond_to?(key.to_sym) ? send(key.to_sym) : nil
  end

  protected
    def add_association name, value
      eigenclass.send :attr_accessor, name.to_sym
      send (name.to_s+"=").to_sym, value
      eigenclass.send :public, name.to_sym #else the accessor will be protected too
      eigenclass.send :public, (name.to_s+"=").to_sym
    end
end

some_model_controller.rb

  def by_department
    @a_object = AssociativeObject.new params[:associative_object]
    @a_object[:from] ||= Date.today - 2.months
    @a_object[:to] ||= Date.today
    @a_object[:department_id] ||= 2 #default to PS R&D
    @results = SomeModel.find_by_department_from_and_to @a_object.department_id, @a_object.from, @a_object.to
  end

view.html.erb

<%= form_for @a_object, url:some_model_path do |f| %>
  <%= f.collection_select :department_id, Department.all, :id, :name %>
  <%= f.text_field :from, class:"date" %>
  <%= f.text_field :to, class:"date" %>
  <%= f.submit  "Search" %>
<% end %>