Ruby on Rails 4基本训练错误ActionController::ParameterMissing in SubjectsController#create

Question

我正在参加来自Lynda.com的Ruby on Rails 4基本培训，并在这个错误中运行：

SubjectsController#create中缺少ActionController：：参数

我基本上有一个具有3个输入的表单：:name、:position和:visible。我可以很好地输入信息，但是当我点击提交按钮时，我得到了错误。以下是服务器的输出：

​

   `Started POST "/subjects/create" for 127.0.0.1 at 2014-11-11 18:02:12 -0500
Processing by SubjectsController#create as HTML
  Parameters: {"utf8"=>"√", "authenticity_token"=>"f6+AdWN3jWO6mL9jrPDgVGoAm/NTBF1GPxGasTaqMh0=", "subject"=>{"name"
=>"Default", "position"=>"5", "visible"=>"false"}, "commit"=>"Create Subject"}
   (0.0ms)  BEGIN
  SQL (1.0ms)  INSERT INTO `subjects` (`created_at`, `name`, `position`, `updated_at`) VALUES ('2014-11-11 23:02:12'
, 'Default', 5, '2014-11-11 23:02:12')
   (4931.3ms)  COMMIT
Redirected to http://localhost:3000/subjects/create?actions=index
Completed 302 Found in 4941ms (ActiveRecord: 4932.3ms)


Started GET "/subjects/create?actions=index" for 127.0.0.1 at 2014-11-11 18:02:17 -0500
Processing by SubjectsController#create as HTML
  Parameters: {"actions"=>"index"}
Completed 400 Bad Request in 1ms

ActionController::ParameterMissing (param is missing or the value is empty: subject):
  app/controllers/subjects_controller.rb:40:in `subject_params'
  app/controllers/subjects_controller.rb:18:in `create'

​

​

SubjectsController

    class SubjectsController < ApplicationController

  layout false

  def index
    @subjects = Subject.sorted
  end

  def show
    @subject = Subject.find(params[:id])
  end

  def new
    @subject = Subject.new({:name => "Default"})
  end

  def create
    @subject = Subject.new(subject_params)
    if @subject.save

      redirect_to(:actions => 'index')
      # raise params.inspect
    else
      render('new')
    end
  end


  def edit
  end

  def delete
  end

  private
    def subject_params
      # same as using "params[:subject]", except that it:
      # - raises an error if :subject is not present
      # - allows listed attributes to be mass-assigned
      params.require(:subject).permit(:name, :position, :visible)
    end


end

​

从服务器输出看，我并没有将:visible属性传递给数据库，即使数据显示在索引页上，即使在出错之后也是如此。

Answer 1

我不认为:visible是问题所在，看看你的日志，你会得到这个错误：

ActionController::ParameterMissing (param is missing or the value is empty: subject):
  app/controllers/subjects_controller.rb:40:in `subject_params'
  app/controllers/subjects_controller.rb:18:in `create'

这是因为这一行：

Started GET "/subjects/create?actions=index" for 127.0.0.1 at 2014-11-11 18:02:17 -0500
Processing by SubjectsController#create as HTML
  Parameters: {"actions"=>"index"}

看起来你正在重定向到GET /subjects/create并传入参数actions=index，这可能是由你的控制器中的这一行引起的：

redirect_to(:actions => 'index')

我认为你在这里的意思是:action (单数)：

redirect_to(:action => 'index')

关于:visible没有被保存的问题，在不了解模型的情况下，我不能说太多，visible在数据库模式中声明了吗？