尝试在Rails中验证表单时出错

Question

我尝试在rails中验证表单。我有一个名为Vehicle的模型，我想确保Plate字段是必需的。这是模型中的代码：

class Vehicle < ActiveRecord::Base
  mount_uploader :image, PictureUploader
  validates_presence_of :plate
end

当我尝试注册新的vehicle时，我收到以下错误：

NoMethodError in Vehicles#create
Showing /home/damaroja/webapps/gestaller/gestaller/app/views/vehicles/_form.html.erb where line #28 raised:

undefined method `map' for nil:NilClass

系统告诉我，我没有错误方法。这怎么可能？

这是_form.html.erb

<%= form_for(@vehicle) do |f| %>
   <% if @vehicle.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@vehicle.errors.count, "error") %> prohibited this  vehicle from being saved:</h2>

      <ul>
      <% @vehicle.errors.full_messages.each do |message| %>
        <li><%= message %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="field">
    <%= f.label :image %><br>
    <%= f.file_field :image %>
  </div>
  <div class="field">
    <%= f.label :plate %><br>
<%= f.text_field :plate %>
  </div>
  <div class="field">
    <%= f.label :places %><br>
    <%= f.number_field :places %>
  </div>
  <div class="field">
    <%= f.label :type %><br>
    <%= f.select 'make', options_for_select(@listadotipos) %>
  </div>
  <div class="field">
   <%= f.label :mam %><br>
    <%= f.text_field :mam %>

.......

这是控制器代码：

  def create
    @vehicle = Vehicle.new(vehicle_params)
   @vehicle.save
    respond_with(@vehicle)
  end

  def new
    @vehicle = Vehicle.new
        tipos= Type.all
        @listadotipos=[]
        tipos.each do |h|
          @listadotipos.push(h.name)
        end
    respond_with(@vehicle)
 end