当用户单击从DropBox中选择并选择文件并单击提交时,我向Rails发起Ajax请求,方法为add_file_via_dropBox.在这个方法中,我通过Paperclip gem的帮助将DropBox文件的URL上传到Amazon S3服务器.

当用户单击取消时,我想要删除部分上传到S3文件,该文件将在content.attachment属性中存储(成功上载后).但是当他点击取消时 – 文件仍在上传(否则他将看不到取消链接),我不知道如何立即删除它.

我的另一个想法是,我可以简单地将取消的属性添加到内容,然后不显示任何内容,其中这样的属性== true.但是这种方法不会让我免于在Amazon S3上浪费空间,所以我应该每天运行一些后台任务来删除已取消的附件.
我宁愿不首先将它们保存在S3上.可能吗？我想将控制器的动作add_file_via_dropBox移动到后台作业,所以我可以在收到客户端的取消ajax请求后立即将其删除.我对这一切有点困惑.你怎么解决这个问题？谢谢.

product_form.html.erb

$.ajax({

  // Cancel file uploading on client side via jqXHR.abort()
  // It's quite useless because with 99% probability that request     
  // already was sent to Rails and is processing by appropriate action

  beforeSend: function(jqXHR,options) {
    tmpl.find('a').click(function(e) {
      e.preventDefault();
      jqXHR.abort();
      $(this).parents('li').remove();
    });
  },type: "POST",dataType: "json",url: "<%= add_file_via_dropBox_url %>",data: { product_id: $("#fileupload").data("product_id"),file: dropBox_file },})

// When Rails response is returned - update UI with "successful upload state"
.done(function(json_file) {
  var done_tmpl = $(tmpl("template-download",json_file));
  var li = $(".files_list").find('[data-uuid="' + json_file.uuid + '"]');
  li.replaceWith(done_tmpl);
}
})

product_controller.rb

# This method is called by Ajax request
def add_file_via_dropBox
  product = Product.find(params[:product_id])

  # Each Product has_many Contents(files)
  file = params[:file]
  content = product.contents.build
  content.attachment_remote_url = file[:url]
  content.save

  # Construct json response object for Ajax call
  json_obj = []
  json_obj << {name: content.attachment_file_name,size: content.attachment_file_size,url: content.attachment.url,thumbnailUrl: content.attachment.url,deleteUrl: "#{root_url}profile/products/delete_content/#{product.id}/#{content.id}",deleteType: "DELETE",uuid: file[:uuid]}

  respond_to do |format|
    format.json { render json: json_obj }
  end
end

content.rb

class Content
  attr_reader :attachment_remote_url
  has_attached_file :attachment,bucket: ENV['S3_BUCKET_NAME']

  def attachment_remote_url=(url_value)
    self.attachment = URI.parse(url_value)
  end
end

加上以后

我更详细地调查了Paperclip的工作原理：

1)当这行代码执行时

content.attachment_remote_url = file[:url]

此paperclip代码从paperclip /…/ uri_adapter.rb执行
哪个从给定的URL下载文件(在我的示例中为DropBox URL)并将其保存在本地(在Rails服务器的临时文件中)

class UriAdapter < AbstractAdapter
  def initialize(target)
    @target = target
    @content = download_content # <----
    cache_current_values
    @tempfile = copy_to_tempfile(@content)
  end

...

def download_content
  open(@target) # method from 'open-uri' library
end

2)仅当我在此处@R_771_301@时,此文件才会被推送到S3：

content.attachment_remote_url = file[:url]
content.save # <----

将调用Paperclip保存方法：(paperclip /…/ attachment.rb)

def save
  flush_deletes unless @options[:keep_old_files]
  flush_writes # <-----
  @dirty = false
  true
end

然后flush_writes将本地文件推送到S3(paperclip /…/s3.rb)

def flush_writes    
  # omitted code       
  s3_object(style).write(file,write_options) # method from `aws-sdk` gem
  # omitted code                 
  end

因此,我将原来的问题缩小到这两个：

1)当它已经在运行时(文件正在下载到我的Rails服务器),如何取消对open(@target)的调用

2)当文件从我的Rails服务器上传到S3时,如何取消对s3_object(样式).write(file,write_options)的调用？