improve how ActiveRecord::Observer defines callbacks on observed models

Instead of using a single `notify_observers` call for every callback type,
each observer now registers a unique callback for itself. Example:

  before_save :_notify_user_observer_for_before_save

  def _notify_user_observer_for_before_save
    observer.update(:before_save, self)
  end

Benefit: "before" callbacks halt when `observer.update` returns false.
This way, ActiveRecord observers can prevent records from saving.

[#4087 state:committed]

Signed-off-by: Jeremy Kemper <jeremy@bitsweat.net>

0 files changed, 0 insertions, 0 deletions