输入后，Rails覆盖数据库中的值

Question

当前，我在覆盖数据库中的值时遇到问题。

提供商可以设置每种葡萄酒的库存量，例如23种，现在前端用户可以选择不同的葡萄酒，例如3瓶。

现在，我要将库存值从23更新为20。如果库存为0，我要禁用定购按钮。

我正在考虑使用read_attribute（attr_name）和write_attribute（attr_name，value）。这是正确的方法吗？

这是我的预订控制人：

class ReservationsController < ApplicationController
  before_action :authenticate_user!
  before_action :set_reservation, only: [:approve, :decline]

  def create
    wine = Wine.find(params[:wine_id])

    if current_user == wine.user
      flash[:alert] = "Du kannst nicht deinen eigenen Wein kaufen!"
    else

    start_date = Date.parse(reservation_params[:start_date])

    @reservation = current_user.reservations.build(reservation_params)
    @reservation.wine = wine
    @reservation.price = wine.price
    @reservation.total = wine.price * @reservation.bottle
    # @reservation.save

  if @reservation.save
    if wine.Reservieren?
      flash[:notice] = "Anfrage versendet!"
  else
    @reservation.Bearbeitung!
    flash[:notice] = "Eroflgreich bestellt!"
  end
else
    flash[:alert] = "Can't make a reservation!"
  end

  end
    redirect_to wine
  end

  def your_orders
    @orders = current_user.reservations.order(start_date: :asc)
  end

  def your_reservations
    @wines = current_user.wines
      redirect_to root_path unless current_user.admin == true
      @count = Reservation.count(:all)
      @total = Reservation.sum(:total)
  end

  def your_upcoming_reservations
    @wines = current_user.wines
      redirect_to root_path unless current_user.admin == true
  end


  def approve
    @reservation.Versendet!
    redirect_to your_reservations_path
    redirect_to root_path unless current_user.admin == true
  end

  def decline
    @reservation.Abgelehnt!
    redirect_to your_reservations_path
    redirect_to root_path unless current_user.admin == true
  end

  # Each Order Details
  def order_details
    @orders = current_user.reservations.order(start_date: :asc)
  end

  private

  def set_reservation
    @reservation = Reservation.find(params[:id])
  end

  def reservation_params
    params.require(:reservation).permit(:start_date, :bottle, :in_stock)
  end
end

我的预订视图：

<div class="panel panel-default">
  <div class="panel-heading" style="text-align:center">
  <span class="price-period" style="border:none; font-size:12px">1 Flasche<br/><%= @wine.price %> €</span>
  <span class="price-period" style="font-size:14px">3 Flaschen<br/><%= @wine.price * 3 %> €</span>
  <span class="price-period" style="font-size:12px">6 Flaschen<br/><%= @wine.price * 6 %> €</span>
  </div>
  <div class="panel-body">
    <%= form_for([@wine, @wine.reservations.new]) do |f| %>
      <div class="panel-body">
        <div class="col-md-12">
          <label>Lieferdatum</label>
          <%= f.text_field :start_date, readonly: true, placeholder: "Lieferdatum", class: "form-control datepicker" %>
        </div>
        <!-- BUY SET? -->
        <div class="col-md-12 select" style="margin-top:10px">
          <div class="form-group">
            <label>Anzahl an Flaschen</label>
            <%= f.select :bottle, wine_quantity(@wine), {}, id: "bottles", prompt: "Auswählen...", class: "form-control" %>
        </div>
      </div>
      </div>

      <div id="preview" style="display:none">
        <table class="reservation-table">
          <tbody>
            <tr>
              <td>Preis pro Flasche</td>
              <td class="text-right"><%= @wine.price %>€</td>
            </tr>
            <tr>
              <td>Anzahl Flaschen</td>
              <td class="text-right">x <span id="reservation_bottles"></span></td>
            </tr>
            <tr>
              <td class="total">Gesamt</td>
              <td class="text-right"><span id="reservation_total"></span>€</td>
            </tr>
          </tbody>
        </table>
      </div>
      <br/>
      <!-- Disable Button if in_stock = 0 -->
      <% if @wine.Sofort? %>
      <%= f.submit "Bestellen", id: "btn_book", class: "btn btn-normal btn-block", disabled: true %>
      <% else %>
      <%= f.submit "Reservieren", id: "btn_book", class: "btn btn-normal btn-block", disabled: true %>
      <% end %>
    <% end %>
  </div>
</div>

<script>

$(function() {

  $.ajax({
    url: '<%= preload_wine_path(@wine) %>',
    dataTyp: 'json',
    success: function(data) {

      var bottles = document.getElementById("bottles").value;
      var total = bottles * <%= @wine.price %>
      $('#reservation_bottles').text(bottles);
      $('#reservation_total').text(total.toFixed(2));

      $('#reservation_start_date').datepicker({
        dateFormat: 'dd-mm-yy',
        minDate: 2,
        maxDate: '5d',
        beforeShowDay: $.datepicker.noWeekends,
        onSelect: function(selected) {
          $('#preview').show();
          $('#btn_book').attr('disabled', false);

          $('#bottles').on('click', function() {
          var bottles = $(this).val();
          var total = bottles * <%= @wine.price %>

          $('#reservation_bottles').text(bottles);
          $('#reservation_total').text(total.toFixed(2));

          });
        }
      });
    }
  });
});

</script>