关于ruby on rails：使用HABTM关联编辑对象在通过ActiveAdmin验证之前修改数据库

Edit object with HABTM association modify database before validation with ActiveAdmin

我在尝试更新具有has_and_belongs_to_many关联的模型时遇到问题。

假设Post has_and_belongs_to_many Tag和Post验证标题和Tags的存在。
如果我更新Post，删除其标题和标签，则在title和Tags中会收到验证错误，
但是ActiveAdmin已经删除了在Post和Tag之间建立关联的记录，因此，如果我离开Post编辑页面，则Post在数据库中将保持无效，而没有Tags。

这里是我的模特：

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class Tag < ActiveRecord::Base
attr_accessible :label
has_and_belongs_to_many :posts
end

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class Post < ActiveRecord::Base
attr_accessible :content, :title, :tag_ids
has_and_belongs_to_many :tags
validates_presence_of :content, :title, :tags
end

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ActiveAdmin.register Post do

form do |f|
f.inputs do
f.input :title
f.input :content
f.input :image
f.input :tags
end

f.buttons
end
end

我使用选择的Railsruby，它允许用户取消选择所有帖子标签。

总而言之，我的问题是：ActiveAdmin在执行模型验证之前更新数据库上的关系。

有针对此行为的解决方案，或者我做错了什么？

编辑：

当我尝试更新不带标题和标签的帖子时，出现以下请求日志：

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Started PUT"/admin/posts/8" for 127.0.0.1 at 2013-04-01 10:32:07 -0300
Processing by Admin::PostsController#update as HTML
Parameters: {"utf8"=>"?","authenticity_token"=>"amSbLlP/rgDrNn/N8lgq/KEaRXK1fMPShZDwpZ0QIJ4=","post"=>{"title"=>"","content"=>"content","tag_ids"=>["",""]},"commit"=>"Update Post","id"=>"8"}
AdminUser Load (0.2ms) SELECT `admin_users`.* FROM `admin_users` WHERE `admin_users`.`id` = 1 LIMIT 1
Post Load (0.2ms) SELECT `posts`.* FROM `posts` WHERE `posts`.`id` = 8 LIMIT 1
Tag Load (0.2ms) SELECT `tags`.* FROM `tags` INNER JOIN `posts_tags` ON `tags`.`id` = `posts_tags`.`tag_id` WHERE `posts_tags`.`post_id` = 8
(0.1ms) BEGIN
SQL (12.3ms) DELETE FROM `posts_tags` WHERE `posts_tags`.`post_id` = 8 AND `posts_tags`.`tag_id` IN (1, 2)
(49.6ms) COMMIT
(0.1ms) BEGIN
(0.2ms) ROLLBACK
Post Load (0.3ms) SELECT `posts`.* FROM `posts` WHERE `posts`.`id` = 8 LIMIT 1
Tag Load (0.2ms) SELECT `tags`.* FROM `tags`
Rendered /home/rodrigo/.rvm/gems/ruby-1.9.3-p125@blog/gems/activeadmin-0.5.1/app/views/active_admin/resource/edit.html.arb (192.3ms)
Completed 200 OK in 276ms (Views: 194.8ms | ActiveRecord: 63.3ms)

编辑2：

好的，我确定ActiveAdmin出现此错误。

从ActiveRecord的行为来看，我认为仅使用模型类会破坏验证流程。请参见以下示例：

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1.9.3p125 :064 > post = Post.find(8)
Post Load (0.3ms) SELECT `posts`.* FROM `posts` WHERE `posts`.`id` = 8 LIMIT 1
=> #<Post id: 8, title:"title", content:"content", created_at:"2013-03-27 13:13:20", updated_at:"2013-03-27 13:13:20", image:"extrato.bmp">
1.9.3p125 :065 > post.tags
Tag Load (0.2ms) SELECT `tags`.* FROM `tags` INNER JOIN `posts_tags` ON `tags`.`id` = `posts_tags`.`tag_id` WHERE `posts_tags`.`post_id` = 8
=> [#<Tag id: 1, label:"tag", created_at:"2013-02-25 18:32:45", updated_at:"2013-02-25 18:32:45">, #<Tag id: 2, label:"new", created_at:"2013-02-25 18:32:50", updated_at:"2013-02-25 18:32:50">]
1.9.3p125 :066 > post.title =""
=>""
1.9.3p125 :067 > post.save #<<<<<<< It's invalid on title
=> false
1.9.3p125 :068 > post.tags = [] #<<<<<<< This shouldnt trigger database update
(0.3ms) BEGIN
SQL (0.5ms) DELETE FROM `posts_tags` WHERE `posts_tags`.`post_id` = 8 AND `posts_tags`.`tag_id` IN (1, 2)
(55.5ms) COMMIT
=> []
1.9.3p125 :069 > post.save #<<<<<<< It's invalid on title AND TAGS
(0.2ms) BEGIN
(0.2ms) ROLLBACK
=> false
1.9.3p125 :070 > post.reload
Post Load (0.2ms) SELECT `posts`.* FROM `posts` WHERE `posts`.`id` = 8 LIMIT 1
=> #<Post id: 8, title:"title", content:"content", created_at:"2013-03-27 13:13:20", updated_at:"2013-03-27 13:13:20", image:"extrato.bmp">
1.9.3p125 :071 > post.valid? #<<<<<<< Now, I have this model in invalid state
Tag Load (0.6ms) SELECT `tags`.* FROM `tags` INNER JOIN `posts_tags` ON `tags`.`id` = `posts_tags`.`tag_id` WHERE `posts_tags`.`post_id` = 8
=> false

是否可以在进行任何数据库更新之前更新帖子属性(包括标签)并验证模型？

相关讨论

您可以使用以下gem：https：//github.com/MartinKoerner/deferred_associations

延迟的关联将修复此错误。

@Rodrigo我可以在没有活动管理员的情况下在本地重现您的问题，实际上，这是使用HABTM关系时的默认操作之一，如果您看到[here] [1]

[1]：http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html#method-i-has_and_belongs_to_many，它说：

collection =对象

1	Replaces the collection’s content by deleting and adding objects as appropriate.

因此，显然您需要覆盖此操作

这里是一个例子：

在has_many：through关系上重写ActiveRecord <<运算符，以接受联接模型的数据

让我知道如何为您提供帮助

因此，对于遇到相同问题的任何人，我都找到了一种解决方法：
您可以在has_and_belongs_to_many关联中定义一个before_remove，并引发一个异常，然后您可以在ActiveAdmin中捕获该异常。

为此它将是

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class Post < ActiveRecord::Base
attr_accessible :content, :title, :tag_ids
has_and_belongs_to_many :tags, before_remove: :check_something
validates_presence_of :content, :title, :tags
end

def check_something(agent)
if self.tags.size == 1
raise ActiveModel::MissingAttributeError.new 'something'
end
end

更多信息：https://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html

我建议添加一个tmp变量并将值存储在其中。然后，如果通过验证，则应将它们移至数据库。

这里是一个例子：

您的models/article.rb：

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class Article < ActiveRecord::Base
validate :author_presence
has_and_belongs_to_many :authors

attr_writer :tmp_author_ids

def tmp_author_ids
@tmp_author_ids || author_ids
end

def author_presence
if tmp_author_ids.reject(&:blank?).empty?
errors.add(:tmp_author_ids, 'Author is missing')
else
self.author_ids = tmp_author_ids
end
end
end

您的admin/article.rb，块form：

1	f.input :tmp_author_ids, as: :select, multiple: true, collection: Author.all, label: 'Authors'

就这样

如果需要，您可以在active_admin中重新定义更新操作，以防止以这种样式保存空标签

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ActiveAdmin.register Post do

controller do
def update
if params[:post][:tag_ids] == ["",""]
flash.now[:alert] ="You can't remove all tags"
render :edit
else
super
end
end
end
...
end

我认为可以删除模型中的这些内容

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attr_accessor :new_tag_ids

validate :validate_new_tags_ids

after_save :update_tags

def update_tags
self.tag_ids = @new_tag_ids if defined?(@new_tag_ids)
@new_tag_ids = nil
end

private
def validate_new_tags_ids
errors[:tags] <<"can't be blank (2)" if @new_tag_ids.blank?
end