PublicActivity で 通知

activity.rb

class Activity < ::PublicActivity::Activity
  has_many :notifications, dependent: :destroy
end

notifiable.rb

module Notifiable
  extend ActiveSupport::Concern
  include PublicActivity::Model

  def self.included(base)
    base.has_many :activities, class_name: Activity, as: :trackable
  end

  def notify_activity(key, owner, users)
    activity = create_activity key, owner: owner
    users.each do |user|
      user.notifications.create(activity: activity)
    end
  end
end

notification.rb

class Notification < ApplicationRecord
  belongs_to :activity
  belongs_to :user

  scope :unread, -> { where(read: false) }

  [
    :trackable, :trackable_id, :trackable=
  ].each { |method| delegate method, to: :activity }

  def unread?
    !read
  end

  def render(context, params)
    activity.render context, params.merge(locals: { notification: self, n: self })
  end
end