rails应用程序中的ActionController :: ParameterMissing

Question

在控制器中获取缺少的参数信息。这是控制器的代码

class SubjectsController < ApplicationController
  layout false
  def new
    @subject=Subject.new
  end
  def create
    @subject = Subject.create(subject_params)
    if @subject.save
      redirect_to(:action => 'index')
    else
      render('new')
    end
  end
  private
  def subject_params
    params.require(:subject).permit(:name, :position, :visible)
  end
end

这是new.html.erb的代码

<%= link_to("<< Back to List", {:action => 'index'}, :class => 'back-link') %>

<div class="subjects new">
  <h2>Create Subject</h2>

  <%= form_for(:subject, :url => {:action => 'create'}) do |f| %>

    <table summary="Subject form fields">
      <tr>
        <th>Name</th>
        <td><%= f.text_field(:name) %></td>
      </tr>
      <tr>
        <th>Position</th>
        <td><%= f.text_field(:position) %></td>
      </tr>
      <tr>
        <th>Visible</th>
        <td><%= f.text_field(:visible) %></td>
      </tr>
    </table>

    <div class="form-buttons">
      <%= submit_tag("Create Subject") %>
    </div>

  <% end %>
</div>

希望有人能够告诉我为什么会收到此错误：

ActionController::ParameterMissing in SubjectsController#create
param is missing or the value is empty: subject
Extracted source (around line #34):
  def subject_params
    params.require(:subject).permit(:name, :position, :visible)
  end
end

由于

Answer 1

请尝试以下代码。这似乎也适用于rails 4。

 #app/views/subjects/_form.html.erb
    <%= form_for(@subject) do |f| %>
      <div class="field">
        <%= f.label :name %><br>
        <%= f.text_field :name %>
      </div>
      <div class="field">
        <%= f.label :position %><br>
        <%= f.text_field :position %>
      </div>
      <div class="field">
        <%= f.label :visible %><br>
        <%= f.text_field :visible %>
      </div>
      <div class="actions">
        <%= f.submit %>
      </div>
    <% end %>

  #app/controllers/subjects_controller.rb
    class SubjectsController < ApplicationController
      layout false
      def new
        @subject = Subject.new
      end

      def index
        @subjects = Subject.all
      end

      def create
        @subject = Subject.new(subject_params)
        if @subject.save
          redirect_to subjects_path
        else
          render :new
        end
      end


      private
      def subject_params
        params.require(:subject).permit(:name, :position, :visible)
      end
    end

检查控制台输出：

Answer 2

你可以试试这个

class SubjectsController < ApplicationController
  layout false

 def index
   @subjects = Subject.scoped
 end  

  def new
    @subject=Subject.new
  end

  def create
    @subject = Subject.new(subject_params)
    if @subject.save
      redirect_to(:action => 'index')
    else
      render('new')
    end
  end
  private
  def subject_params
    params.require(:subject).permit(:name, :position, :visible)
  end
end

在视图中

<%= link_to("<< Back to List", {:action => 'index'}, :class => 'back-link') %>

<div class="subjects new">
  <h2>Create Subject</h2>

  <%= form_for @subject do |f| %>

    <table summary="Subject form fields">
      <tr>
        <th>Name</th>
        <td><%= f.text_field(:name) %></td>
      </tr>
      <tr>
        <th>Position</th>
        <td><%= f.text_field(:position) %></td>
      </tr>
      <tr>
        <th>Visible</th>
        <td><%= f.text_field(:visible) %></td>
      </tr>
    </table>

    <div class="form-buttons">
      <%= submit_tag("Create Subject") %>
    </div>

  <% end %>
</div>

在路线/config/routes.rb

中

resources :subjects