Detect changes with update_attributes

Rails
1

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

2

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

On 1 March 2010 08:26, LeonS [email protected] wrote:

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3

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?

4

On 1 March 2010 09:06, LeonS [email protected] wrote:

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.