更新记录，涉及Join Table

Question

Ruby on Rails 4

我有一个表格来编辑记录。形式与创建新记录相同。 （措辞除外）。当我单击提交时，它给出了 nilLNilClass。我的代码适用于更新我的其他不涉及联接表的记录，所以我不确定出了什么问题。

形式：

<%= form_for(@test) do |f| %>

<div class="field">
  <%= f.label :name %><br>
  <%= f.text_field :name %>
</div>
<div class="field">
  <%= f.label :type %><br>
  <%= f.text_field :type %>
</div>
<div class="field">
  <%= f.label :category %><br>
<%= f.select :category, [ ["IP Voice Telephony", "ip_voice"], ["IP Video Surveillance", "ip_video_surveillance"], ["IP Video Telephony", "ip_video_telephony"], ["Enterprise Gateways", "enterprise_gateways"], ["Consumer ATAs", "consumer_atas"], ["IP PBX", "ip_pbx"] ], {prompt: "Select Category"}, class: "input-lg", :id => "category" %>
</div>
<div class="field">
  <%= f.label :description %><br>
  <%= f.text_field :description %>
</div>

<div id="container" style="width:1140px; margin-left: auto; margin-right: auto;">
<button type="button" class="reset">Reset Search</button>
<table width="100%" class="tablesorter">
<thead>
  <tr>
  <th width="5%" class="filter-false"><input type="checkbox" onClick="toggle(this)"></th>
  <th width="37%" data-placeholder="Search">Content</th>
  <th width="10%" data-placeholder="Search">Type</th>
  <th width="10%" data-placeholder="Search">Category</th>
  <th width="10%" data-placeholder="Search">Product</th>
  <th width="10%" data-placeholder="Search">User</th>
  <th width="8%" data-placeholder="Search">Active</th>
  </tr>
</thead>

<tbody>
  <% @questions.each do |q| %>
  <tr>
    <td><%= check_box_tag "test[question_ids][]", q.id, @test.question_ids.include?(q.id) %></td>
    <td><%= q.content %></td>
    <td><%= q.question_type %></td>
    <td><%= q.category %></td>
    <td>GXP</td>
    <td><%= q.user_id %></td>
    <td><%= q.active %></td>
  </tr>
  <% end %>
 </tbody>
</table>

<br>
</div>
<div class="actions">
  <%= f.submit "Update Test", class: "btn btn-lg btn-primary" %>
</div>
<% end %>

控制器：

before_action :set_test, only: [:show, :edit, :update, :destroy]  
before_action :signed_in_user, only: [:index, :edit, :show, :update, :destroy]

def edit
  @test = Test.find(params[:id])
  @questions = Question.all
end

def update
  respond_to do |format|
    if @test.update(test_params)
      format.html { redirect_to @test, notice: 'Test was successfully updated.' }
      format.json { head :no_content }
    else
      format.html { render action: 'edit' }
      format.json { render json: @test.errors, status: :unprocessable_entity }
    end
  end
end

def test_params
    params.require(:test).permit(:name, :user_id, :type, :category, :description, :question_ids => [], questions_attributes: [ :id ] ).
    merge user_id: current_user.id
end  

错误：

Started PATCH "/tests/98" for 127.0.0.1 at 2014-05-20 10:12:58 -0400
Processing by TestsController#update as HTML
Parameters: {"utf8"=>"✓", "authenticity_token"=>"x=", "test"=>{"name"=>"one two three four, spelling YEah!!", "type"=>"", "category"=>"ip_voice", "description"=>"not so smart, wooops", "question_ids"=>["1"]}, "commit"=>"Update Test", "id"=>"98"}
Test Load (0.3ms)  SELECT "tests".* FROM "tests" WHERE "tests"."id" = ? LIMIT 1  [["id", "98"]]
User Load (0.2ms)  SELECT "users".* FROM "users" WHERE "users"."remember_token" = 'x' LIMIT 1
Completed 500 Internal Server Error in 6ms

NoMethodError (undefined method `update' for nil:NilClass):
app/controllers/tests_controller.rb:56:in `block in update'
app/controllers/tests_controller.rb:55:in `update'

这是第 56 行：if @test.update(test_params)

我确实认为我必须在 edit() 中定义 @test 很奇怪。我也试过 @test.save 有同样的错误。我误会了什么。

Answer 1

您需要在update 操作中定义@test。目前它没有定义，所以它的值是nil，你会收到错误。

在update 操作中添加这一行，然后调用@test.update：

@test = Test.find(params[:id])

我看到您有一个用于设置测试的before_action 回调，即set_test。在这种情况下，您不需要

@test = Test.find(params[:id])

在update 行动中。您需要做的就是在before_action 回调中添加update 操作：

before_action :set_test, only: [:show, :edit, :update, :destroy]  

另外，我建议您从edit 操作中删除 @test 设置，因为您已经在before_action 回调中添加了edit 操作

最后，set_test（最好是private 方法）方法应如下所示：

def set_test
  @test = Test.find(params[:id])
end

Answer 2

你需要在你的控制器中这样做

before_action :set_test, only: [:show,:edit,:update,:destroy] 和你的控制器的末尾

private

def set_test

@test = Test.find(params[:id])

end

另外，像这样更新你的编辑方法

def edit
  #@test = Test.find(params[:id]) remove this line you wont need it.
  @questions = Question.all
end

或

您可以按照 @kirti Thorat 的回答。