Detect changes with update_attributes

Hi,

how can i detect changed attributes, when i'm using update_attributes
in the update method of my controller?
A solution in the model would be very nice. Tanks

greetings
Leon

You can do it with update_attributes as that updates and saves in one go.

You can do this instead

@thing.attributes=(params[:thing])
if @thing.changed?
  @thing.save
else
  ....something else
end

All the best

RobL

Hi,

I thought about your solution and now I think i've got a better
solution, what do you think about that?
I just overwrite the update_attributes method and after i assigned the
attributes, i can check for changes.

def update_attributes(attributes)
    self.attributes = attributes
    if self.changed?
      #kickoff something....
    end
    save
  end

What do you think about this solution?

The problem with both yours and Rob's solution is that you're doing
your post-update checks in one place, when there's more than one place
those updates can happen. Your modification of Rob's suggestion is
better, because at least you're checking in the model, rather than in
the controller.

But you might be better off doing your check regardless of where the
updates have come from (either a single attribute being assigned, or a
mass allocation), so put a "before_save" filter in your model:

  before_save :check_changed
  def check_changed
    puts (changed? ? "changed" : "unchanged")
  end

Of course, this might *cause* problems for your specific requirement,
if, for instance, there's certain fields you want to ignore changes
for. But you can always expand the "check_changed" method to do more
work; check the changed_attributes hash, etc.