Question

I have the following model (sort_timestamp is a datetime):

class Post < ActiveRecord::Base
  [snip attr_accessible]
  acts_as_nested_set
  after_create :set_sort_timestamp

  private
  def set_sort_timestamp
    self.sort_timestamp = self.created_at
  end
end

I’m using https://github.com/collectiveidea/awesome_nested_set . This code doesn’t set sort_timestamp. What am I doing wrong?

Answer 1

Unless I’m missing the point of what you’re doing here, you’re probably looking for before_create if you’d like it to save when the row is created. Otherwise you’ll have to add self.save to the method, but that will cause extra database calls, so before_create might be the better option.

(Basically, the flow of what you were doing before was that the model would be created, saved to the database, and then the object would modify its attribute sort_timestamp to be created_at; this is after your database commit, and only performed in memory (so not persisted, unless you were persisting it in another way later in the code).

EDIT: Actually, this probably won’t work because created_at probably won’t be set before the record is created. A few options:

1) Add self.save to end of your method with after_create
2) Use Time.now if the times sort_timestamp and created_at don’t have to be exactly the same.
or, 3) Try adding default value to migration: How to use created_at value as default in Rails