Rails 与蜻蜓的交易

Question

我目前正在做一个 Rails 项目。我有一个嵌套表单，允许用户上传多张图片。我正在使用蜻蜓进行上传我还对用户可以上传的图像的大小和格式设置了一些限制，并且它们工作正常。我的问题是，当我尝试上传无效图像时，即使它们不会被上传，表单的其余部分仍会被保存。为了缓解这个问题，我最初编写了如下创建方法：

def create
  @announcements = Announcement.new(announcement_params)
  images = []

  respond_to do |format|
    params[:photos]['image'].each do |pic|
    img = Photo.new(image: pic)
    if img.valid?
      images << img
    else
      @photos = @announcement.photos.build
      format.html { render: 'new' }
    end

    if @announcement.save
      params[:photos]['image'].each do |pic|
        @photos = @announcement.photos.create(image: pic)
      end
      format.html { redirect_to @announcement }
    else
      format.html { render: 'new' }
    end
  end

end

这很好用，但我相信你们中的很多人都会同意其中有很多重复，而且代码很丑陋。在找到更好的解决方案之前，我会写一个代码作为快速解决方法。我尝试使用如下交易：

def create
  @announcement = Announcement.new(announcement_params)

  respond_to do |format|
    ActiveRecord::Base.transaction do
      begin
        @announcement.save
        params[:photos]["image"].each do |pic|
          @photos = @announcement.photos.create!(image: pic)
        end
        format.html { redirect_to @announcement }
      rescue
        format.html { render action: 'new' }
      end
    end
end

结束

但它不起作用任何人都可以告诉我我做错了什么，或者建议更好的方法来做到这一点。谢谢

编辑：这是我的日志的摘录：

Started POST "/announcements" for 127.0.0.1 at 2015-09-20 15:07:31 +0100

AnnouncementsController 处理#create as HTML 参数：{"utf8"=>"✓",

"authenticity_token"=>"fjU1kjnxqSdDwTqieOpTTCH56//p65AynqNyQQX6yiu84zwO0bJeQ3ZKr8tEBvGSZJphclxKkoys2bFp771hWg==", "announcement"=>{"title"=>"Testing wrong image size", "content"=>"Testing wrong image format with transaction code "}, "photos"=>{"image"=>[#<ActionDispatch::Http::UploadedFile:0x007fe9a83f9b18 @tempfile=#<Tempfile:/tmp/RackMultipart20150920-10097-muom0i.jpg>, @original_filename="AhiiZFK2.jpg", @content_type="image/jpeg", @headers="Content-Disposition: form-data; name=\"photos[image][]\"; filename=\"AhiiZFK2.jpg\"\r\nContent-Type: image/jpeg\r\n">]}, "commit"=>"Créer l'announce"}
  User Load (0.6ms)  SELECT  "users".* FROM "users" WHERE "users"."id" =   ORDER BY "users"."id" ASC LIMIT 1  [["id", 1]]
   (0.3ms)  BEGIN
  SQL (0.9ms)  INSERT INTO "announcements" ("title", "content", "created_at", "updated_at") VALUES (, , , ) RETURNING "id"  [["title", "Testing wrong image size"], ["content", "Testing wrong image format with transaction code "], ["created_at", "2015-09-20 14:07:31.247186"], ["updated_at", "2015-09-20 14:07:31.247186"]]
DRAGONFLY: shell command: 'identify' '-ping' '-format' '%m %w %h' '/tmp/RackMultipart20150920-10097-muom0i.jpg'
   (41.4ms)  COMMIT
  Photo Load (0.8ms)  SELECT "photos".* FROM "photos" WHERE "photos"."announcement_id" =   [["announcement_id", 1]]
  Rendered announcements/new.html.erb within layouts/application (24.1ms)
  Rendered layouts/_header.html.erb (1.9ms)
  Rendered layouts/_sidebar.html.erb (0.5ms)
Completed 200 OK in 3287ms (Views: 3154.3ms | ActiveRecord: 44.1ms)

Answer 1

如果您不希望数据库中的数据在记录无效时出现，您需要中止交易。这是在引发异常时完成的。但是你嵌套你的代码的方式，一个来自 create! 的异常被拯救了，事务块可以正常完成。

你需要这样嵌套：

begin
  ActiveRecord::Base.transaction do
    @announcement.save!
    params[:photos]["image"].each do |pic|
      @announcement.photos.create!(image: pic)
    end
  end # transaction
  format.html { redirect_to @announcement }
rescue
  logger.warn "transaction aborted"
  format.html { render action: 'new' }
end

为了进一步改进，您将数据库的东西放在一个自己的方法中，这样数据库调用和渲染调用就不会混在一起。

要显式中止（或用数据库术语 "rollback"）事务，您可以引发 ActiveRecord::Rollback 异常。这会中止交易并且不会重新抛出交易块之外。 http://api.rubyonrails.org/classes/ActiveRecord/Rollback.html

Rails 与蜻蜓的交易

Rails transaction with dragonfly

ruby

ruby-on-rails

dragonfly-gem

ruby-on-rails-4