Sample Code

notifications.rb

module Api
  class NotificationsController < ApiController
    before_action :authorize_request

    def index
      notifications = current_user.notifications.recent

      json = NotificationSerializer.new(notifications, is_collection: true).serializable_hash

      render json: json
    end

    def mark_as_seen
      current_user.notifications.mark_as_seen!
    end
  end
end

reviews.rb

def index
    playground = Playground.find params[:playground_id]
    reviews = playground.reviews.desc_order.limit(5)
    render json: reviews
  end

  def create
    review = PlaygroundReview.new review_params
    review.user = current_user

    if review.save
      OwnerReservationMailer
          .with(owner: review.playground_owner, playground: review.playground, review: review)
          .new_review_mail
          .deliver_later

      review.playground_owner.notifications.create({
                                               title: 'Playground Review',
                                               message: "New review for #{review.playground&.name}."
                                             })
    end

    render json: {
      ok: true,
      review: review
    }
  end