appointment_observer.rb

class AppointmentObserver < ActiveRecord::Observer
  def after_save(appointment)
    user = appointment.user

    return unless user.notifiable?

    if appointment.initial?
      MailService.welcome_email(user).deliver
    elsif appointment.second_visit? && !user.has_logged_in?
      MailService.second_chance_email(user).deliver
    else
      MailService.post_appointment_email(user).deliver
    end
  end
end