在另一个模型中渲染具有嵌套属性的模型的部分内容

Question

我有一个为房屋建模的 Rails 应用程序。 house 包含 rooms，rooms 具有 light 和 small_appliance 的嵌套属性。我有一个计算器控制器，这是最终用户访问应用程序的方式。

我的问题是，我无法从 calculator 中获取添加 rooms 的部分内容以正确渲染和提交。初始页面允许用户输入house 信息，单击提交时使用save_house 保存该信息。这还会将用户重定向到 add_rooms 页面，他们可以在其中向房屋添加房间。

add_rooms 显示正确，但是当我单击提交时，出现此错误：

RuntimeError in Calculator#add_room

Showing app/views/calculator/add_rooms.html.erb where line #2 raised:

Called id for nil, which would mistakenly be 4 -- if you really wanted the id of nil, use object_id

Extracted source (around line #2):

1: <div id="addRooms">
2:   <p>House id is <%= @house.id %></p>
3:   
4:   <h3>Your rooms:</h3>
5:   <% if @house.rooms %>

RAILS_ROOT: C:/Users/ryan/Downloads/react
Application Trace | Framework Trace | Full Trace

C:/Users/ryan/Downloads/react/app/views/calculator/add_rooms.html.erb:2:in `_run_erb_app47views47calculator47add_rooms46html46erb'
C:/Users/ryan/Downloads/react/app/controllers/calculator_controller.rb:36:in `add_room'
C:/Users/ryan/Downloads/react/app/controllers/calculator_controller.rb:33:in `add_room'

这对我来说很奇怪，因为当 add_rooms 首次呈现时，它显示 house_id.我不明白为什么表单提交后没有通过。

代码如下：

app/models/room.rb

class Room < ActiveRecord::Base
  # schema { name:string, house_id:integer }
  belongs_to :house
  has_many :lights, :dependent => :destroy
  has_many :small_appliances, :dependent => :destroy
  validates_presence_of :name
  accepts_nested_attributes_for :lights, :reject_if => lambda { |a| a.values.all?(&:blank?) }, :allow_destroy => true
  accepts_nested_attributes_for :small_appliances, :reject_if => lambda { |a| a.values.all?(&:blank?) }, :allow_destroy => true         
end

app/models/house.rb

class House < ActiveRecord::Base
  has_many :rooms

  # validation code not included

  def add_room(room)
    rooms << room
  end

end

app/controllers/calculator_controller.rb

class CalculatorController < ApplicationController
  def index
  end

  def save_house
    @house = House.new(params[:house])
    respond_to do |format|
      if @house.save
        format.html { render :action => 'add_rooms', :id => @house }
        format.xml { render :xml => @house, :status => :created, :location => @house }
      else
        format.html { render :action => 'index' }
        format.xml  { render :xml => @house.errors, :status => :unprocessable_entity }
      end
    end
  end

  def add_rooms
    @house = House.find(params[:id])
    @rooms = Room.find_by_house_id(@house.id)

  rescue ActiveRecord::RecordNotFound
    logger.error("Attempt to access invalid house #{params[:id]}")
    flash[:notice] = "You must create a house before adding rooms"
    redirect_to :action => 'index'
  end

  def add_room
    @room = Room.new(params[:room])
    @house = @room.house

    respond_to do |format|
      if @room.save
        flash[:notice] = "Room \"#[email protected]}\" was successfully added."
        format.html { render :action => 'add_rooms' }
        format.xml { render :xml => @room, :status => :created, :location => @room }
      else
        format.html { render :action => 'add_rooms' }
        format.xml  { render :xml => @room.errors, :status => :unprocessable_entity }
      end
    end
  rescue ActiveRecord::RecordNotFound
    logger.error("Attempt to access invalid house #{params[:id]}")
    flash[:notice] = "You must create a house before adding a room"
    redirect_to :action => 'index'
  end

  def report
    flash[:notice] = nil
    @house = House.find(params[:id])
    @rooms = Room.find_by_house_id(@house.id)
  rescue ActiveRecord::RecordNotFound
    logger.error("Attempt to access invalid house #{params[:id]}")
    flash[:notice] = "You must create a house before generating a report"
    redirect_to :action => 'index'
  end

end

app/views/calculator/add_rooms.html.erb

<div id="addRooms">
  <p>House id is <%= @house.id %></p>

  <h3>Your rooms:</h3>
  <% if @house.rooms %>
  <ul>
    <% for room in @house.rooms %>
    <li>
      <%= h room.name %> has <%= h room.number_of_bulbs %> 
      <%= h room.wattage_of_bulbs %> watt bulbs, in use for 
      <%= h room.usage_hours %> hours per day.
    </li> 
    <% end %>
  </ul>
  <% else %>
  <p>You have not added any rooms yet</p>
  <% end %>  

  <%= render :partial => 'rooms/room_form' %>

  <br />
</div>

<%= button_to "Continue to report", :action => "report", :id => @house %>

app/views/rooms/_room_ form.html.erb

<% form_for :room, @house.rooms.build, :url => { :action => :add_room } do |form| %>
  <%= form.error_messages %>
  <p>
    <%= form.label :name %><br />
    <%= form.text_field :name %>
  </p>

  <h3>Lights</h3>
  <% form.object.lights.build if form.object.lights.empty? %>
  <% form.fields_for :lights do |light_form| %>
    <%= render :partial => "light", :locals => { :form => light_form } %>
  <% end %>
  <p class="addLink"><%= add_child_link "[+] Add new light", form, :lights %></p>

  <h3>Small Appliances</h3>
  <% form.object.small_appliances.build if form.object.small_appliances.empty? %>
  <% form.fields_for :small_appliances do |sm_appl_form| %>
    <%= render :partial => "small_appliance", :locals => { :form => sm_appl_form } %>
  <% end %>
  <p class="addLink"><%= add_child_link "[+] Add new small appliance", form, :small_appliances %></p>

  <p><%= form.submit "Submit" %></p>
<% end %>

application_helper.rb

module ApplicationHelper
  def remove_child_link(name, form)
    form.hidden_field(:_delete) + link_to_function(name, "remove_fields(this)")
  end

  def add_child_link(name, form, method)
    fields = new_child_fields(form, method)
    link_to_function(name, h("insert_fields(this, \"#{method}\", \"#{escape_javascript(fields)}\")"))
  end

  def new_child_fields(form_builder, method, options = {})
    options[:object] ||= form_builder.object.class.reflect_on_association(method).klass.new
    options[:partial] ||= method.to_s.singularize
    options[:form_builder_local] ||= :form
    form_builder.fields_for(method, options[:object], :child_index => "new_#{method}") do |form|
      render(:partial => options[:partial], :locals => { options[:form_builder_local] => form })
    end
  end
end

谢谢，
瑞安

Answer 1

出于好奇，为什么不让 house 接受房间的嵌套属性。这将使您的控制器代码更简单，因为添加许多房间、灯光和小家电就像执行 @house.update_attributes(params[:house]) 一样简单。然而，这并不是一个有帮助的答案，因为如果您进行更改，您仍然会遇到当前的问题。

您的第一个错误来自 app/views/calculator/_room_form.html.erb

<% form_for :room, :url =>; 的第一行{：动作=> :add_room, :id => @house } 做 |form| %>

您没有为 form_for 提供对象，因此 add_child 调用 new_child_fields 方法
_link 尝试在 Nil 类上调用reflect_on_association。

解决方案是将行更改为

<% form_for :room, @house.rooms.build, :url => {：动作=> :add_room } 做 |form| %>

这可以让您简化控制器，因为与房屋关联的房间已经传递给它。

def add_room
    @room = Room.new(params[:room])
    @house = @room.house
    respond_to do |format|
      if @room.save
        flash[:notice] = "Room \"#[email protected]}\" was successfully added."
        format.html { render :action => 'add_rooms' }
        format.xml { render :xml => @room, :status => :created, :location => @room }
      else
        format.html { render :action => 'add_rooms' }
        format.xml  { render :xml => @room.errors, :status => :unprocessable_entity }
      end
    end
  rescue ActiveRecord::RecordNotFound
    logger.error("Attempt to access invalid house #{params[:id]}")
    flash[:notice] = "You must create a house before adding a room"
    redirect_to :action => 'index'
  end

我相信你的第二个错误是同样的问题。然而，因为您调用的是 has_many 访问器而不是生成 nil，所以您传递的是一个空数组，这解释了错误消息的差异。同样，解决方案是在渲染之前构建一个轻小型设备（如果尚不存在）。

  <h3>Lights</h3>
  <% form.object.lights.build if form.object.lights.empty? %>
  <% form.fields_for :lights do |light_form| %>
    <%= render :partial => 'rooms/light', :locals => { :form => light_form } %>
  <% end %>
  <p class="addLink"><%= add_child_link "[+] Add new light", form, :lights %></p>

  <h3>Small Appliances</h3>
  <% form.object.small_appliances.build if form.object.small_appliances.empty? %>
  <% form.fields_for :small_appliances do |sm_appl_form| %>
    <%= render :partial => 'rooms/small_appliance', :locals => { :form => sm_appl_form } %>
  <% end %>

您的新错误来自于此：

 def new_child_fields(form_builder, method, options = {})
    options[:object] ||= form_builder.object.class.reflect_on_association(method).klass.new

    # specifically this line. 
    options[:partial] ||= method.to_s.singularize

    options[:form_builder_local] ||= :form
    form_builder.fields_for(method, options[:object], :child_index => "new_#{method}") do |form|
      render(:partial => options[:partial], :locals => { options[:form_builder_local] => form })
    end
  end

new_child_fields 假设 _light 部分位于 app/views/calculators 文件夹中

解决方案是将 light 和small_appliances 部分移动到此文件夹或修改您的辅助方法以接受部分选项。