Returns whether an instance can be deleted or not.

environment.rb

require 'instance_helpers'
ActiveRecord::Base.send(:include, InstanceHelpers)

instance_helpers.rb

module InstanceHelpers
  public
  # Extends ActiveRecord. Returns false if an has any associated object.
  # You can pass a list of association names to be ignored, 
  # e.g. @user.can_be_deleted?(:ignore => [:addresses, :phones])
  def can_be_deleted?(options={})
    options[:ignore] ||= []
    # Check for single model associations using: present?
    ho = self.class.reflect_on_all_associations :has_one
    assocciated_model_names = ho.map{ |obj| obj.name } - options[:ignore]
    return false if assocciated_model_names.any?{ |a| self.send(a).present? }
    # Avoid DB overhead by using: count.zero? for collection associations
    habtm = self.class.reflect_on_all_associations :has_and_belongs_to_many
    hm = self.class.reflect_on_all_associations :has_many
    aggregate_objs = habtm + hm
    aggregate_obj_names = aggregate_objs.map{|obj| obj.name } - options[:ignore]
    !aggregate_obj_names.any?{ |a| !self.send(a).count.zero? }
  end
end