application_controller.rb

class ApplicationController < ActionController::Base

  def load_resource
    parent = nil
    request.path.split("/").select{|p| !p.blank?}.to_pairs.each do |obj|
      parent = set_instance_variable(obj.first.singularize, obj.last, parent)
    end
    
    model_name = params[:controller].split('/').last.singularize
    begin
      set_instance_variable(model_name, params[:id], parent) unless params[:action] == "index" || !instance_variable_get("@#{model_name}").nil?
    rescue NameError, NoMethodError => e
      instance_variable_set("@#{model_name}", model_name.to_sym)
    end
  end
  
  def set_instance_variable(model_name, id_or_action, parent_obj=nil)
    logger.debug("LOADING : #{model_name}/#{id_or_action}")
    if id_or_action.to_i != 0
      temp = parent_obj.nil? ? model_name.camelcase.constantize.find(id_or_action.to_i) : parent_obj.send(model_name.pluralize).find(id_or_action.to_i)
      instance_variable_set("@#{model_name}", temp)
    else
      temp = parent_obj.nil? ? model_name.camelcase.constantize.new(params[model_name.to_sym]) : parent_obj.send(model_name.pluralize).build(params[model_name.to_sym])
      instance_variable_set("@#{model_name}", temp)
    end
    temp
  end

end

core_extensions.rb

class Array
  def to_pairs
    (0..(length/2)-1).collect {|i| [self[i*2], self[i*2+1]]}
  end
end