javascript - 主干和 Rails 关联 : Avoiding JSON HashWithIndifferentAccess errors

Question

我试图让我的主干关联在 Rails 应用程序中工作，但我在尝试更新现有模型时遇到了困难。具体来说，Rails 会抛出以下错误:

Started PUT "/posts/2" for 127.0.0.1 at 2012-01-04 02:36:14 +1000
Processing by PostsController#update as JSON Parameters: {"post"=>{"content"=>"Seconderona", "created_at"=>"2012-01-03T10:51:09Z", "id"=>2, "title"=>"Second test post", "updated_at"=>"2012-01-03T10:51:09Z", "comments"=>[{}]}, "id"=>"2"} Post Load (0.2ms) SELECT "posts".* FROM "posts" WHERE "posts"."id" = ? LIMIT 1 [["id", "2"]] WARNING: Can't mass-assign protected attributes: id Completed 500 Internal Server Error in 15ms

ActiveRecord::AssociationTypeMismatch (Comment(#70104367824560) expected, got ActiveSupport::HashWithIndifferentAccess(#70104367278120)):
app/controllers/posts_controller.rb:62:in block in update'<br/>
app/controllers/posts_controller.rb:61:inupdate'

一些事情:

这是触发于(例如):

c = window.router.comments.models[0]
c.save({content: 'Changed content'})

此外，是的，模型中存在“accepts_nested_attributes_for”。

下面的(有问题的)代码几乎是从 thoughtbot 的“rails Backbone ”电子书中逐字提取的，我也尝试过遵循 Backbone 关系 gem 的文档。两者都会引发此错误。任何想法表示赞赏，下面的代码

RAILS“发布”模型

class Post < ActiveRecord::Base
  has_many :comments

  accepts_nested_attributes_for :comments

  def as_json(options = nil)
    super((options || {}).merge(include: { comments: { only: [content] } } ))
  end
end

RAILS“评论”模型

class Comment < ActiveRecord::Base
  belongs_to :post

  accepts_nested_attributes_for :post

  def as_json(options = nil)
    super((options || {}).merge(include: { post: { only: [:title, :content]}}))
  end
end

Backbone 后 Controller

class Backbonerelationaldemo.Models.Post extends Backbone.Model
  paramRoot: 'post'

  initialize: () ->
    comments = new Backbonerelationaldemo.Collections.CommentsCollection
    comments.reset(@get('comments'))
    @setComments(comments)

  setComments: (comments) ->
    @comments = comments


class Backbonerelationaldemo.Collections.PostsCollection extends Backbone.Collection
  model: Backbonerelationaldemo.Models.Post
  url: '/posts'

Backbone 评论 Controller

class Backbonerelationaldemo.Models.Comment extends Backbone.Model
  paramRoot: 'comment'

  initialize: () ->
    if (@has('post')) 
      @setPost(new Backbonerelationaldemo.Models.Post(@get('post')))

  setPost: (post) ->
    @post = post

class Backbonerelationaldemo.Collections.CommentsCollection extends Backbone.Collection
  model: Backbonerelationaldemo.Models.Comment
  url: '/comments'

Answer 1

我最近处理了同样的问题。它实际上不是 HashWithIndifferentAccess 错误:它与 accepts_nested_attributes_for 期望参数的方式有关。

当您声明 accepts_nested_attributes_for :comments 时，Rails 会在传入的参数上查找参数调用 comments_attributes。

问题是来自 Backbone 的 JSON 表示具有 "comments" 属性，而不是 "comments_attributes" 属性。

您可以通过向您的 Post 模型添加一个 toJSON 函数来在 Backbone 端修复它:

# in your Post model
toJSON: ->
  attrs = _.clone(@attributes)
  attrs.comments_attributes = _.clone(@attributes.comments)
  delete attrs.comments
  attrs

或者您可以在 Rails Controller 中处理它:

# in your Posts controller
def update
  params[:comments_attributes] = params.delete(:comments) if params.has_key? :comments
  # call to update_attributes and whatever else you need to do
 end

希望这对您有所帮助。