paranoid ActiveRecord models (See related posts)

ActiveRecord::Base.class_eval do
  alias_method :destroy!, :destroy
  
  class << self
    alias_method :find_with_deleted, :find
    alias_method :count_with_deleted, :count
    
    def find(*args)
      if [:all, :first].include?(args.first)
        constrain = "#{table_name}.deleted_at IS NULL"
        constrains = (scope_constrains.nil? or scope_constrains[:conditions].nil? or scope_constrains[:conditions] == constrain) ?
          constrain :
          "#{scope_constrains[:conditions]} AND #{constrain}"
        constrain(:conditions => constrains) { return find_with_deleted(*args) }
      end
      find_with_deleted(*args)
    end
    
    def count(conditions = nil, joins = nil)
      constrain(:conditions => "#{table_name}.deleted_at IS NULL") { count_with_deleted(conditions, joins) }
    end
  end
  
  def destroy
    update_attribute(:deleted_at, self.class.default_timezone == :utc ? Time.now.utc : Time.now) unless new_record?
    freeze
  end
end

ActiveRecord::Associations::HasAndBelongsToManyAssociation.class_eval do
  alias_method :find_with_deleted, :find
  def find(*args)
    constrain(:conditions => "#{@join_table}.deleted_at IS NULL") { find_with_deleted(*args) }
  end
end