module ActiveRecord::NoTouching

def applied_to?(klass) #:nodoc:
  klasses.any? { |k| k >= klass }
end

def apply_to(klass) #:nodoc:
  klasses.push(klass)
  yield
ensure
  klasses.pop
end

def klasses
  Thread.current[:no_touching_classes] ||= []
end

def no_touching?
  NoTouching.applied_to?(self.class)
end

def touch(*)
  super unless no_touching?
end