Rails - Dec 2005 - Setter not being called

I have written the followign setter to raise an exception when the field 
disabled_on is beeing assigned a value minor or equal that the enabled_on 
field.

class Survey < ActiveRecord::Base
  def disabled_on=(date)
  	raise AssignmentException if date != nil and date <= self.enabled_on
  	write_attribute(:disabled_on, date)
  end
end

The matter is that this method never gets called, as I can assure adding a 
breakpoint() as its first line.

I''ve also written a test to check for this exception:

assert_raise (AssignmentException) {
	@survey.disabled_on = @survey.enabled_on
}

Of course this test doesn''t pass, becouse the disabled_on=() method
never is
called.

Any clues ?

TIA,

ckozus.

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