生成文件并使用RubyZip下载为zip

Question

对于我的Ruby on Rails项目(Rails版本5.1.2(，我正在生成图像文件(png(并使用RubyZip gem将它们下载为zip文件。

图像文件不存储在任何目录中。我有一个名为附件的模型。每个附件都有一个属性image_string，该属性是图像的 base64 字符串。您可以使用类似 image_tag(src = "data:image/jpeg;base64, #{attachment.image_string}", style: "border-radius: 0;") 的标记来显示图像

对于多个图像，我想为每个图像创建临时文件，而无需将它们存储在任何地方，并将这些图像下载为 zip 文件。

我现在拥有的代码：

def bulk_download
  require('zip')
  ::Zip::File.open("/tmp/mms.zip", Zip::File::CREATE) do |zipfile|
    Attachment.all.each do |attachment|
      image_file = Tempfile.new("#{attachment.created_at.in_time_zone}.png")
      image_file.write(attachment.image_string)
      zipfile.add("#{attachment.created_at.in_time_zone}.png", image_file.path)
    end
  end
  send_file "/tmp/mms.zip", type: 'application/zip', disposition: 'attachment', filename: "my_archive.zip"
  respond_to do |format |
    format.all { head :ok, content_type: "text/html" }
  end
end

但是下载的zip文件中没有文件，大小为0字节。提前谢谢。

Answer 1

您应该需要关闭并取消链接 zip 文件，如下所示：

require('zip')
class SomeController < ApplicationController
  # ...
  def bulk_download
    filename = 'my_archive.zip'
    temp_file = Tempfile.new(filename)
    begin
      Zip::OutputStream.open(temp_file) { |zos| }
      Zip::File.open(temp_file.path, Zip::File::CREATE) do |zip|
        Attachment.all.each do |attachment|
          image_file = Tempfile.new("#{attachment.created_at.in_time_zone}.png")
          image_file.write(attachment.image_string)
          zipfile.add("#{attachment.created_at.in_time_zone}.png", image_file.path)
        end
      end
      zip_data = File.read(temp_file.path)
      send_data(zip_data, type: 'application/zip', disposition: 'attachment', filename: filename)
    ensure # important steps below
      temp_file.close
      temp_file.unlink
    end
  end
end

这是我用作此代码源代码的一篇很好的博客文章：https://thinkingeek.com/2013/11/15/create-temporary-zip-file-send-response-rails/

此外，最好将所有库要求保留在文件顶部(即 require('zip')(。

Answer 2

接受的解决方案确实是正确的。但是，我将扩展已经提供的解决方案，使其与ActiveStorage附件一起使用。
在使用公认的解决方案时，我发现image_string方法不适用于ActiveStorage附件并引发这样的错误

NoMethodError - undefined method `image_string' for #<ActiveStorage::Attached::One:0x00007f78cc686298>

假设我们有一个名为 Product 的 rails 模型，其 ActiveStorage 属性名为 attachment

class Product < ApplicationRecord
  has_one_attached :attachment
end

为了使它适用于ActiveStorage附件，我们需要更新代码，如下所示

begin
  Zip::OutputStream.open(temp_file) { |zos| }
  Zip::File.open(temp_file.path, Zip::File::CREATE) do |zipfile|
    Product.all.each do |product|
      image_file = Tempfile.new("#{product.attachment.created_at.in_time_zone}.png")
      
    # image_file.write(product.attachment.image_string) #this does not work for ActiveStorage attachments
      
      # use this instead
      File.open(image_file.path, 'w', encoding: 'ASCII-8BIT') do |file|
        product.attachment.download do |chunk|
          file.write(chunk)
        end
      end
      zipfile.add("#{product.attachment.created_at.in_time_zone}.png", image_file.path)
    end
  end
  zip_data = File.read(temp_file.path)
  send_data(zip_data, type: 'application/zip', disposition: 'attachment', filename: filename)
ensure # important steps below
  temp_file.close
  temp_file.unlink
end

Answer 3

它对我有用(我需要加载基于Carrierwave的MyModel文档(：

require 'zip'
require 'open-uri'
class TestsController < ApplicationController
  def index
    filename = 'test.zip'
    temp_file = ::Tempfile.new(filename)
    my_model_document = ::MyModel.last
    my_model_document_name = ::File.basename(my_model_document.document.path)
    begin
      ::Zip::OutputStream.open(temp_file) { |zos| }
      ::Zip::File.open(temp_file.path, ::Zip::File::CREATE) do |zipfile|
        dr_temp_file = Tempfile.new(my_model_document_name)
        dr_temp_file.write(open(my_model_document.document.url).read.force_encoding("UTF-8"))
        zipfile.add(my_model_document_name, dr_temp_file.path)
      end
      zip_data = File.read(temp_file.path)
      send_data(zip_data, type: 'application/zip', disposition: 'attachment', filename: filename)
    ensure
      temp_file.close
      temp_file.unlink
    end
  end
end