Method telling whether an ActiveRecord has been newly created (and already persisted)?

[Eugene Gilburg]

Several times I found myself of need of a method that tells whether an ActiveRecord instance has just been created. For example, when writing generic activity logging code that needs to know whether model is newly created as opposed to updated, but the invocation is in a service outside of the model itself and thus I can't just write `after_create` and `after_update` hooks, except perhaps just to set custom flags for the service to inspect.

It's not the same as `new_record?` because `new_record?` is only true before record is saved, not after save. I'm thinking `newly_created?` or `just_created?` name. Calling it `created?` would be too ambiguous and higher chance to clash with similarly named method by application developers in their own code.

Essentially `new_record?` to `newly_created?` is the same as `marked_for_destruction?` is to `destroyed?`, or as `changes` is to `previous_changes`.

In my app I've implemented the code like this:

def newly_created?
  id_changes = previous_changes['id']
  id_changes && id_changes.last && !id_changes.first
end

Is this something anyone else found doing, and would it be helpful for ActiveRecord to provide this method?

[Colin Law]

Not entirely sure exactly what you mean by newly created. Do you mean
not updated since created (in which case you could compare created_at
and updated_at) or only just recently created (in which case you could
compare created_at to time now) or created within the current request
(in which case just remember in code that you have just created it) or
something else.

Colin

[Bayram Kuliyev]

First of all you should give a rigour definition of "newly_created?". I mean, what should we consider "newly created"? A record created 1 second ago?  10 mins ago, or 1 day ago?

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