How to "update_attributes" without executing "before_save"?

Question

I have a before_save in my Message model defined like this:

   class Message < ActiveRecord::Base
     before_save lambda { foo(publisher); bar }
   end

When I do:

   my_message.update_attributes(:created_at => ...)

foo and bar are executed.

Sometimes, I would like to update message's fields without executing foo and bar.

How could I update, for example, the created_at field (in the database) without executing foo and bar ?

Lucifer

Answer 1

In rails 3.1 you will use update_column.

Otherwise:

In general way, the most elegant way to bypass callbacks is the following:

class Message < ActiveRecord::Base
  cattr_accessor :skip_callbacks
  before_save lambda { foo(publisher); bar }, :unless => :skip_callbacks # let's say you do not want this callback to be triggered when you perform batch operations
end

Then, you can do:

Message.skip_callbacks = true # for multiple records
my_message.update_attributes(:created_at => ...)
Message.skip_callbacks = false # reset

Or, just for one record:

my_message.update_attributes(:created_at => ..., :skip_callbacks => true)

If you need it specifically for a Time attribute, then touch will do the trick as mentioned by @lucapette .

Nomen

Looks like a good general solution! One question: What exactly Message.batch = true do ? – Lucifer

It is just a flag. You can replace it by whatever you want. – Nomen

This won't work on serialized columns (update_column, that is), as it skips serialization / deserialization as well for some reason. – Thence

Worth noting that using update_column will also mean validations are not run. – Lamdin

Since you are setting an attribute on the class, this doesn't seem very thread-safe. Thoughts? – Legist

Answer 2

update_all won't trigger callbacks

my_message.update_all(:created_at => ...)
# OR
Message.update_all({:created_at => ...}, {:id => my_message.id})

http://apidock.com/rails/ActiveRecord/Base/update_all/class

Ecthyma

my_message.update_all(:created_at => ...) issues a syntax error, but the second option works fine! – Lucifer

my_message.update_all will trigger undefined method update_all. Message.update_all will do the trick – Enplane

You might be able to use increment_counter [if it's a counter you want to increment] which also skips callbacks, I believe. – Brave

to work with instance you can use update_column or update_columns for avoid callback calls – Jardiniere

Answer 3

Use the touch method. It's elegant and does exactly what you want

Sushi

Looks like almost what I need. The new value of created_at in my case is not the current time. – Lucifer

@Misha you're obviously right. So you can use api.rubyonrails.org/classes/ActiveRecord/… :D – Sushi

@lucapette: How? The docs says that update_attribute invokes the callbacks. – Lucifer

@Misha you can't. Thinking about your problem I was confusing callbacks with validation... So I think you should use update_all. By the way see edgeguides.rubyonrails.org/… maybe there is something i'm overlooking – Sushi

Answer 4

update_column or update_columns is the closest method to update_attributes and it avoids callbacks without having to manually circumvent anything.

Aeneid

api.rubyonrails.org/classes/ActiveRecord/… – Duenna

Answer 5

You could also make your before_save action conditional.

So add some field/instance variable, and set it only if you want to skip it, and check that in your method.

E.g.

before_save :do_foo_and_bar_if_allowed

attr_accessor :skip_before_save

def do_foo_and_bar_if_allowed
  unless @skip_before_save.present?
    foo(publisher)
    bar
  end
end

and then somewhere write

my_message.skip_before_save = true
my_message.update_attributes(:created_at => ...)

Exculpate