Ruby on rails 3 为什么我可以创建一个具有hstore属性的模型，但在尝试更新时却出现500错误？

大量借款于：

创建新模型时，我可以从新视图中定义任意数量的参数my hstore column，并正确设置hstore column并保存模型。太好了

但是，当我尝试编辑和提交时，我得到：

参数'id'应为Hash get字符串

其中“id”是我为创建的参数的hstore键指定的名称

也很有趣…我可以从控制台创建和更新相同的模型，没有问题

WTF

这是我的模型：

class Testmethod < ActiveRecord::Base

  attr_accessible :name, :params

  serialize :params, ActiveRecord::Coders::Hstore

  def as_json(options = {})
    { :name => name, :params => params }
  end

end 

以下是表格：

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

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

<div class="field">
  <%= f.label :name %>
  <%= f.text_field :name %>
</div>

<div class="field">
  <%= f.label :script %>
  <%= f.text_area :script, :rows => 6 %>
</div>

<h4>Parameters</h4>

<div class="well">

<div class='clearfix attributeContainer'>
  <div class='row'>
    <p class='span3 underline'>Name</p>
    <p class='span3 underline'>Value</p>
  </div>
  <% @testmethod.params.try(:each) do |key, value| %>
      <div class="row">
        <p class='span3'>
          <%= text_field_tag key, key, :class => 'text_field dynamicAttributeName' %>
        </p>
        <p class='span3'>
          <%= text_field key, :class => 'text_field', :value => value %>
        </p>
        <p class='span1'>
          <a herf='#' class='btn removeRow'>X</a>
        </p>
      </div>
  <% end %>

  <div class='row attributeTemplate <%= 'hide' if @testmethod.params.present? %>'>
    <p class='span3'>
      <input class='text_field dynamicAttributeName' id='' name='' placeholder='New Attribute name' size='30' type='text' />
    </p>
    <p class='span3'><input class='text_field' id='bar' name='' placeholder='value' size='30'  type='text'  /></p>
    <p class='span1'><a herf='#' class='btn removeRow'>X</a></p>
  </div>
  <%= link_to 'Add Parameter', '#', :class => 'btn addAttribute btn-mini' %>
</div>

</div>

<div class="row">
    <div class="span12">
        <div class="actions">
        <%= f.submit "Save", :class => 'btn btn-primary ' %> or <%= link_to "Cancel", request.referrer || testmethods_path %>
      </div>
    </div>
</div>

<% end %>

<%= content_for :js do %>
<script type='text/javascript'>
   $('.attributeContainer').delegate('.dynamicAttributeName', 'keyup', function(event){
     nameElem  = $(this);
     valueElem = nameElem.closest('.row').children('p').children('.text_field')
     value     = nameElem.val().toLowerCase();
     valueElem.attr('id',          'testmethod_params_' + value       );
     valueElem.attr('name',        'testmethod[params][' + value + ']');
     valueElem.attr('placeholder', 'value for ' + value          );
   })

   $('.attributeContainer').delegate('.removeRow', 'click', function(){
     console.log($(this).closest('.row'))
     $(this).closest('.row').html('');
   })

   $('.addAttribute').on('click', function(){
     contents = "<div class='row'>" + $('.attributeTemplate').html() + '</div>';
     $(this).before(contents);
   })
  </script>
    <% end %>