rails中未定义的方法错误

Question

我是rails的新手，我可以使用一些帮助。 我在rails中有以下设置

Day has_many Bookings
Booking belongs_to Day

shared / _booking_form中的预订表单如下：

   <%= form_for Booking.new do |t| %>
<%= render 'shared/error_messages', object: t.object %>
<div class="field">
  <%= t.label :start %><br>
  <%= t.time_select :start %>
</div>
<div class="field">
  <%= t.label :end %><br>
  <%= t.time_select :end %>
</div>
<div class="field">
  <%= t.label :comentariu %><br>
  <%= t.text_area :comentariu, placeholder: "Adauga un comentariu.."  %>
</div>
<%= t.submit "Post", class: "btn btn-primary" %>
<% end %>

预订控制器看起来像这样

  def show
    @bookings = Booking.all
  end
  def new
    @booking = Booking.new
  end
  def create
    @booking = @day.bookings.build(booking_params)
    @booking.save
      flash[:success] = "Book created!"
      redirect_to root_url
  end

  def destroy
  end

  private

  def booking_params
    params.require(:booking).permit(:start, :end, :comentariu)
  end

我收到此错误，但我无法解决

NoMethodError (undefined method `bookings' for nil:NilClass):
  app/controllers/bookings_controller.rb:9:in `create'

任何帮助都将不胜感激。