请教个 Rails one to many validate 的问题

两个model

area.rb

class Area < ActiveRecord::Base
  has_many  :categories
  
  validates_presence_of :name,  :sort_order
  validates_uniqueness_of :name
end

category.rb

class Category < ActiveRecord::Base
  belongs_to  :area
  has_many    :topics
  
  validates_presence_of   :name,  :sort_order
  validates_uniqueness_of :name
  validates_associated    :area
end

controller:

  def category_new
    @category = Category.new
    @areas = Area.find(:all)
  end

  def category_create
    @category = Category.new(params[:category])
    if @category.save
      flash[:notice] = 'Category was successfully created.'
      redirect_to :action => 'category_list'
    else
      render :action => 'category_new'
    end
  end

view:
category_new.rhtml

<div class="admin-form">
  <fieldset>
  <legend>新建类别</legend>
    <% form_tag :action => 'category_create' do %>
    <%= render :partial => 'category_form' %>
        <%= submit_tag "新建" %>
    <% end %>
  </fieldset>
</div>

<br/>
<%= link_to '返回', :action => 'category_list' %>

_category_form.rhtml

<%= error_messages_for "category" %>

<!--[form:category]-->
<p><label for="category_name">分类名称</label><br/>
<%= text_field 'category', 'name'  %></p>

<p><label for="category_area_id">版区名称</label><br/>
<%= collection_select("category", "area_id" , @areas, "id", "name") %></p> 
</p>

<p><label for="category_sort_order">排序</label><br/>
<%= text_field 'category', 'sort_order'  %></p>

现在的问题是: 如果满足 Category 类的条件, 添加、删除、修改都正常
但是，只要 Category　校验不通过（比如让　分类名称　为空）提交后就提示：

Showing app/views/admin/_category_form.rhtml where line #8 raised:

You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.inject

难道是rails的校验有顺序？google了半天没结果，郁闷

那是因为你在category_create里少了赋值@areas = Area.find(:all) 而在category.save失败后又render了'category_new'，这个view里又render partial用了_category_form.rhtml ，在第8行里用到了@areas这个变量

其实根据你帖的错误提示“Showing app/views/admin/_category_form.rhtml where line #8 raised:”一眼就看到了这个错误，你咋就不仔细瞧瞧错误提示呢？
你是不懂英文呢还是真的不懂英文呢？

谢谢,现在ok了,提示是看懂了,初用rails,语法还觉得比较奇怪,还不适应,再次表示感谢

真没觉得ruby的语法有什么奇怪的地方，一切看上去都是那么自然