calling save on model object does not generate a sql update

I have been using RoRfor a few days, so excuse me if this is a basic
question.

I am trying to save a model object from an action in a controller.

When I call a method on the model object that causes a state change,
then call save, no sql is generated.
However, if I modify the model object property directly from the
controller, then call save, sql is generated.

Here is an example of what I am talking about:

Model object

I have been using RoRfor a few days, so excuse me if this is a basic
question.

I am trying to save a model object from an action in a controller.

When I call a method on the model object that causes a state change,
then call save, no sql is generated.
However, if I modify the model object property directly from the
controller, then call save, sql is generated.

The first thing is that save on an unchanged object is a no-op as of
rails 2.1 (when partial updates was added).

    def modifyModel
            aDate = Date\.today
    end

This method does not change the aDate attribute: it just sets a local
variable called aDate (which is forgotten about as soon as that method
returns). To disambiguate and force ruby to call your accessor you
need to do self.aDate = Date::today

Fred