Question

如果我在Rails中有以下型号，我将如何在Ember / Ember数据中表示这个？

class Attachment < ActiveRecord::Base
  belongs_to :user
  belongs_to :attachable, polymorphic: true
end

class Profile < ActiveRecord::Base
  belongs_to :user
  has_one :photo, class_name: 'Attachment', as: :attachable
end

class Post < ActiveRecord::Base
  belongs_to :user
  has_many :attachments, as: :attachable
end

我发现的参考文献是the relevant ember-data pull request，the ember-data tests for polymorphic relationships和this related question，但很难从中找出一个典型的例子。

Answer 1

我现在使用两种不同的方式来处理rails风格的“多态”模型。我已更新下面的代码以显示两种用途。

Attachment模型：这是Rails方面的“多态”，但总是“嵌入”在Ember方面。原因是我目前只需要保存/更新附件及其相关模型。

Comment模型：这在Rails端和Ember端都是多态的。

我还提供了Post模型的代码，因为它可以包含多个附件和多条评论。

Rails代码：

class Attachment < ActiveRecord::Base
  belongs_to :user
  belongs_to :attachable, polymorphic: true
end

class Comment < ActiveRecord::Base
  belongs_to :user
  belongs_to :commentable, polymorphic: true
end

class Post < ActiveRecord::Base
  belongs_to :user
  has_many :attachments, as: :attachable
  has_many :comments, as: :commentable
end

class ApplicationSerializer < ActiveModel::Serializer
  embed :ids, include: true
end

class AttachmentSerializer < ApplicationSerializer
  attributes :id, :url, :errors
  has_many :comments
end

class CommentSerializer < ApplicationSerializer
  attributes :id, :body, :created_at, :commentable_id, :commentable_type
  has_one :user
end

class PostSerializer < ApplicationSerializer
  attributes :id, :title, :body, :posted_at, :errors
  has_one :user
  has_many :attachments, embed: :objects, include: true
  has_many :comments
end

class Api::V1::PostsController < Api::V1::BaseController
  before_filter :auth_only!, only: :create

  def create
    # clean / capture ember-data supplied arguments
    params[:post].delete(:user_id)
    attachments_params = params[:post].delete(:attachments)

    @post = current_user.posts.new(params[:post])
    process_attachments(attachments_params)

    if @post.save
      render json: @post, status: 201
    else
      warden.custom_failure!
      render json: @post, status: 422
    end
  end

  protected

    def process_attachments(attachments_params)
      return unless attachments_params.present?

      attachments_params.each do |attachment_params|
        # ignore ember-data's additional keys
        attachment_params.delete(:created_at)
        attachment_params.delete(:user_id)

        attachment = @post.attachments.new(attachment_params)
        attachment.user = current_user
      end
    end
end

Ember代码：

DS.RESTAdapter.configure 'App.Post',
  alias: 'Post'

DS.RESTAdapter.map 'App.Post',
  attachments: { embedded: 'always' }

App.Store = DS.Store.extend
  adapter: DS.RESTAdapter.create
    namespace: 'api/v1'

App.Comment = App.Model.extend
  user: DS.belongsTo('App.User')
  commentable: DS.belongsTo('App.Commentable', { polymorphic: true })
  body:       DS.attr('string')
  createdAt:  DS.attr('date')

App.Commentable = App.Model.extend
  comments: DS.hasMany('App.Comment')

App.Attachment = App.Commentable.extend
  user: DS.belongsTo('App.User')
  url: DS.attr('string')

App.Post = App.Commentable.extend
  user: DS.belongsTo('App.User')
  attachments: DS.hasMany('App.Attachment')

  title: DS.attr('string')
  body: DS.attr('string')
  postedAt: DS.attr('date')

App.PostFormOverlayController = App.OverlayController.extend
  # 'files' attribute is set by a widget that wraps the filepicker.io JS
  updateAttachments: (->
    attachments = @get('attachments')
    attachments.clear()
    @get('files').forEach (file) =>
      attachment = App.Attachment.createRecord({fpFile: file})
      attachments.addObject(attachment)
  ).observes('files')

App.CommentNewController = App.ObjectController.extend
  # this should be instantiated with it's model set to the commentable
  # item. eg. `{{render 'comment/new' content}}`

  save: ->
    transaction = @get('store').transaction()
    comment = transaction.createRecord App.Comment,
      body: @get('body')
      commentable: @get('model')

    comment.one 'didCreate', @, ->
      @set('body', null)

    transaction.commit()

不幸的是，我的Rails代码已经变得有点污染了特定于ember数据的怪异，因为它试图发送回模型上定义的所有属性。（注意：只有open proposal的只读属性才能解决params污染问题。

如果有人知道更好的方法来解决上述问题，请告诉我们！

NB：我有点担心从App.Commentable扩展模型会阻止我在模型上有多个多态附件，我可能需要寻找不同的方式处理那个。

Answer 2

Kevin Ansfield的回答（不使用Post部分）的评论部分适用于Ember 1.3.0-beta / Ember Data 1.0.0-beta.4，除了rails序列化器，现在应该是：< / p>

class CommentSerializer < ActiveModel::Serializer
  attributes :id, :body, :created_at, :commentable_id, :commentable_type
  has_one :user

  def attributes
    data = super
    data[:commentable] = {id: data[:commentable_id], type: data[:commentable_type]}
    data.delete(:commentable_type)
    data.delete(:commentable_id)
    data
  end

ember-data中的Rails风格多态模型

2 个答案: