after_create for setting dummy password_digest in case of oauth user with has_secure_password

Question

I'm using has_secure_password with a User model. I'd like to set the password_digest string to a dummy value if the user signed up via oauth. Currently, I am only doing facebook and saving the user with facebook_id. I'd like to add the following similar logic:

class User < ActiveRecord::Base
  has_secure_password
  attr_accessible :facebook_id
  after_create :update_password_digest_if_from_facebook

  def update_password_digest_if_from_facebook
    logger.info "here within update_password_digest_if_from_facebook" # this gets called
    if self.facebook_id # not seen?
      self.password_digest='oauth-account'
      self.save  
    end
    logger.info "there is a facebook_id" if self.facebook_id # this isn't called 
  end
  ...
end

However, the pieces in update_password_digest_if_from_facebook are not being called correctly. Do I have access to self here?

While this is admittedly a hacky way to bypass has_secure_password, why aren't the calls to self.facebook_id being executed? It seems like I should have access to self at this point.

thx in advance