I have a model that has an amount
and I'm tracking to see if this amount is changed with a Model.amount_changed?
with a before_save
which works fine but when I check to see amount_was
and amount_change?
it only returns the updated amount not the previous amount. And all this is happening before it is save. It knows when the attribute is changed but it will not return the old value.
Ideas?
class Reservation < ActiveRecord::Base
before_save :status_amount, :if => :status_amount_changed
def status_amount_changed
if self.amount_changed? && !self.new_record?
true
else
false
end
end
def status_amount
title = "Changed Amount"
description = "to #{self.amount_was} changed to #{self.amount} units"
create_reservation_event(title, description)
end
def create_reservation_event(title, description)
Event.create(:reservation => self, :sharedorder => self.sharedorder, :title => title, :description => description, :retailer => self.retailer )
end
end
If you want to keep track of changes in your model Rails provides "Dirty Objects".
E.g. Your model has a name
attribute:
my_model = MyModel.find(:first)
my_model.changed? # it returns false
# You can Track changes to attributes with my_model.name_changed? accessor
my_model.name # returns "Name"
my_model.name = "New Name"
my_model.name_changed? # returns true
# Access previous value with name_was accessor
my_model.name_was # "Name"
# You can also see both the previous and the current values, using name_change
my_model.name_change #=> ["Name", "New Name"]
If you want to store the old value inside your database, you can use:
amount
amount_was
that retrieve the value of amount before the change.You can save both during the update_attributes
call.
Otherwise, if you don't need the amount_was
history, you can just use two instance variables.
If you need somthing more, like tracking your model history, Rails has a nice dedicated plugin. As for other nice topics Ryan Bates speak about I here: Railscasts #177
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With