Ruby on rails 自引用关联时如何验证子对象属性？

我有一个模型“任务”，有两个实体——“任务”和“子任务”，具有自参考关联

class Task < ActiveRecord::Base
  has_many    :subtasks, class_name: 'Task', foreign_key: 'parent_id', dependent: :destroy
  belongs_to  :parent, class_name: 'Task'
  accepts_nested_attributes_for :subtasks, allow_destroy: true
  validates :title, presence: true, length: { minimum: 3 }
  validates :priority, presence: true, numericality: { only_integer: true }, length: { is: 1 }
  validates_associated :subtasks
end

现在在TaskShow页面上，我可以创建具有有效属性的子任务，也不能创建具有无效属性的子任务，但我没有收到验证消息。 我怎样才能修好它？ 对不起，我的英语不好

PS: 我不知道为什么，但错误存在于控制器中，而不存在于视图中

@project.update_attributes(project_params)
puts @project.errors.full_messages
if @project.errors.empty? || :tasks_attributes?
  redirect_to @project
  puts @project.errors.full_messages

   (0.0ms)  begin transaction
   (0.0ms)  rollback transaction
Tasks title can't be blank
Tasks title is too short (minimum is 3 characters)
Redirected to http://localhost:3000/projects/3
Tasks title can't be blank
Tasks title is too short (minimum is 3 characters)
Completed 302 Found in 6ms (ActiveRecord: 0.2ms)

---

还应将错误消息添加到视图中：

= simple_form_for @task do |t|
= t.simple_fields_for :subtasks, @task.subtasks.build do |f|
   #error message added here
   - if @task.subtasks.errors.any?
     %ul.errors
       - @task.subtasks.errors.full_messages.each do |msg|
       %li= msg
  .form-inputs
    = f.input :title
    = f.hidden_field :priority, value: @task.priority
  .form-actions
    = f.button  :submit, "Add a subtask"

编辑

您的应用程序中有一个_formpartial，请将该代码更改为

= simple_form_for @task do |f|
- if @task.errors.any?
 ul.errors
   - @task.errors.full_messages.each do |msg|
    => msg

= f.input :title
= f.input :description
= f.input :scheduled
= f.input :deadline
= f.input :priority, collection: [["None", 0], ["High", 3], ["Medium", 2], ["Low", 1]], selected: ["None"]
= f.button :submit

---

嗯，我得到了#的

未定义方法“errors”子任务模型中是否有
属于：task
？我只有一个模型-'task'：
有许多子任务，类名称：'task'，外键：'parent\u id'，dependent:：destroy
属于：parent，类名称：'task'
是，我在布局中有它：`-flash.each do | name，msg |=content | tag:div，msg，class:“警报信息”=yield`该死，不能一个字符串一个字符串地编写代码。如果此处的帮助完整代码仅用于显示闪存消息，则答案中的代码用于显示验证错误消息
= simple_form_for @task do |t|
= t.simple_fields_for :subtasks, @task.subtasks.build do |f|
   #error message added here
   - if @task.subtasks.errors.any?
     %ul.errors
       - @task.subtasks.errors.full_messages.each do |msg|
       %li= msg
  .form-inputs
    = f.input :title
    = f.hidden_field :priority, value: @task.priority
  .form-actions
    = f.button  :submit, "Add a subtask"

= simple_form_for @task do |f|
- if @task.errors.any?
 ul.errors
   - @task.errors.full_messages.each do |msg|
    => msg

= f.input :title
= f.input :description
= f.input :scheduled
= f.input :deadline
= f.input :priority, collection: [["None", 0], ["High", 3], ["Medium", 2], ["Low", 1]], selected: ["None"]
= f.button :submit