gistfile1.rb

def get_parent_resource(target_klass, path)
  # Convert the requested path into hash form
  hash = ActionController::Routing::Routes.recognize_path(path, :method => :get)

  # Loop through path keys and see if any end in '_id'
  # and our child class belongs_to the associated AR Class
  pair = hash.detect do |k, v|
    k.to_s.ends_with?("_id") && target_klass.columns_hash.has_key?(k.to_s)
  end

  # Load up the AR class based on the matching path pair
  klass = pair[0].to_s[0...-3].classify.constantize

  # Find and return the target parent object
  klass.find(pair[1])
end