Ruby on Rails - 如何从嵌套模型中委派错误消息答案

【问题标题】：Ruby on Rails - How to delegate error messages from nested modelRuby on Rails - 如何从嵌套模型中委派错误消息
【发布时间】：2015-06-18 18:42:46
【问题描述】：

class User
  include Mongoid::Document

  has_many :images
  accepts_nested_attributes_for :image
end


class Image
  include Mongoid::Document
  include Mongoid::Timestamps
  include Mongoid::Paperclip

  has_mongoid_attached_file :uploaded_image,
    :path => ":rails_root/public/uploads/:class/:id/:basename.:extension",
    :url => "public/uploads/"
    validates_attachment_content_type :uploaded_file, :content_type => "application/png", :message => "error massage"
     belongs_to :user
    delegate :url, :path, to: :uploaded_image, allow_nil: true, prefix: false
end

如果 :uploaded_image 无效，如何将错误从 Image 委托给用户？

例如：

user_image = user.images.build(uploaded_image: new_image.path)
user_image.save

如果上传的图片无效，应该会报错。

【问题讨论】：

标签： ruby-on-rails ruby ruby-on-rails-4 mongoid paperclip

【解决方案1】：

Rails 有 validates_associated 助手（在 Mongoid 中也可用），它将在每个关联对象上调用 valid?。

validates_related 的默认错误消息是“无效”。请注意，每个关联对象都将包含自己的错误收藏;错误不会冒泡到调用模型。

Rails Guides: Active Record Validations

class User
  include Mongoid::Document

  has_many :images
  accepts_nested_attributes_for :image
  validates_associated :images
end

注意不要将validates_associated :user添加到Image，因为这会导致无限循环。

您可以像这样访问嵌套图像的错误：

<% if @user.errors.any? %>
  <div id="error_explanation">
    <h2><%= pluralize(@user.errors.count, "error") %> prohibited this user from being saved:</h2>
    <ul>
    <% @user.errors.full_messages.each do |msg| %>
      <li><%= msg %></li>
    <% end %>
    </ul>
    <% if @user.images.any? %>
    <ul>
      <% @user.images.each do |image| %>
        <% if image.errors.any? %>
        <li>
          <ul>
            <% image.errors.full_messages.each do |msg| %>
            <li><%= msg %></li>
            <% end %>
          </ul>
        </li>
        <% end %>
      <% end %>
    </ul>
    <% end %>
  </div>
<% end %>

【讨论】：