嵌套表单错误 - ArgumentError（参数的错误数目（0代表1））：

Question

我跟随此屏幕截图制作嵌套模型表单。 http://railscasts.com/episodes/196-nested-model-form-part-1

现在，我想我的应用程序包含这样一个嵌套的模型窗体，但我收到了一个参数错误（错误数量的参数（0为1））。

我似乎无法弄清楚我错了什么地方，想寻求一些建议，我可以尝试什么以及为什么会发生一些错误。

错误发生在主题模型中的这一行上。

has_many :lessons, :dependent => destroy 

的其他相关的代码：

主题控制器：

def new 
    @subject = Subject.new 
    #3 times one for lecture one for lab one for tut. 
    3.times{@subject.lessons.build} 

    respond_to do |format| 
     format.html # new.html.erb 
     format.json { render json: @subject } 
     format.js 
    end 
    end 

物体模型

class Subject < ActiveRecord::Base 
    has_many :lessons, :dependent => destroy 
    attr_accessible :lesson_attributes, :acad_unit, :cohort_size, :discipline, :remarks, :subject_code, :subject_name, :year_of_study 
    accepts_nested_attributes_for :lessons, :reject_if => lambda { |a| a[:lesson_type].blank? }, :allow_destroy => true 
end 

课模型

class Lesson < ActiveRecord::Base 
    belongs_to :subject 
    attr_accessible :frequency, :lesson_type, :no_of_lesson, :possible_venues 
end 

_form.html.erb

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

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

    <div class="field"> 
    <%= f.label :subject_code %><br /> 
    <%= f.text_field :subject_code %> 
    </div> 
    <div class="field"> 
    <%= f.label :subject_name %><br /> 
    <%= f.text_field :subject_name %> 
    </div> 
    <div class="field"> 
    <%= f.label :year_of_study %><br /> 
    <%= f.text_field :year_of_study %> 
    </div> 
    <div class="field"> 
    <%= f.label :discipline %><br /> 
    <%= f.text_field :discipline %> 
    </div> 
    <div class="field"> 
    <%= f.label :acad_unit %><br /> 
    <%= f.text_field :acad_unit %> 
    </div> 
    <div class="field"> 
    <%= f.label :cohort_size %><br /> 
    <%= f.text_field :cohort_size %> 
    </div> 
    <div class="field"> 
    <%= f.label :remarks %><br /> 
    <%= f.text_field :remarks %> 
    </div> 

    <ol> 
    <%= f.fields_for :lessons do |builder| %> 
    <%= render "lesson_fields", :f => builder %> 
    <% end %> 
    </ol> 

<% end %> 

_lesson_fields.html.erb

<p> 
<div class="field"> 
    <%= f.label :lesson_type %><br /> 
    <%= f.text_field :lesson_type %> 
    </div> 
    <div class="field"> 
    <%= f.label :no_of_lesson %><br /> 
    <%= f.text_field :no_of_lesson %> 
    </div> 
    <div class="field"> 
    <%= f.label :frequency %><br /> 
    <%= f.text_field :frequency %> 
    </div> 
    <div class="field"> 
    <%= f.label :possible_venues %><br /> 
    <%= f.text_field :possible_venues %> 
    </div> 
</p> 

Answer 1

我想你想：

has_many :lessons, :dependent => :destroy 

？

Here你会发现一个很好的话题讨论。