6

I'm trying to build an API backend for file uploads. I want to be able to upload files with a POST request that has a Base64-encoded string of the file. The server should decode the string, and save the file using CarrierWave. Here's what I have so far:

photo.rb:

class Photo
  include Mongoid::Document
  include Mongoid::Timestamps
  mount_uploader :image_file, ImageUploader
end

image_uploader.rb:

class ImageUploader < CarrierWave::Uploader::Base
  storage :file

  def store_dir
    "uploads/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}"
  end
end

Rails console: (summary)

ruby-1.8.7-p334 :001 > img = File.open("../image.png") {|i| i.read}
 => "\377���JFIF\000\001\002\001\000H\000H\000\000\377�Photoshop 3.0\0008BIM\003...
ruby-1.8.7-p334 :003 >   encoded_img = Base64.encode64 img
=> 3af8A\nmLpplt5U8q+a7G2...
ruby-1.8.7-p334 :005 >   p = Photo.new
 => #<Photo _id: 4e21b9a31d41c817b9000001, created_at: nil, updated_at: nil, _type: nil, user_id: nil, image_file_filename: nil> 
ruby-1.8.7-p334 :006 > p.user_id = 1
 => 1 
ruby-1.8.7-p334 :007 > p.image_file = Base64.decode64 encoded_img
\255��=\254\200�7u\226���\230�-zh�wT\253%����\036ʉs\232Is�M\215��˿6\247\256\177...
ruby-1.8.7-p334 :008 > p.save
 => true 
ruby-1.8.7-p334 :009 > p.image_file.url
 => nil

full

The problem appears to be related to the process of converting a Base64-decoded string to a file. CarrierWave seems to expect a File object, and instead I'm giving it a String. So how do I convert that String to a File object. I'd like this conversion not to save anything to the file system, simply create the object and let CarrierWave do the rest.

4

3 回答 3

24

CarrierWave 也接受 StringIO，但它需要一个original_filename方法，因为它需要它来计算文件名和进行扩展检查。你如何在 Rails 2 和 3 之间改变，这里有两种方法：

导轨 2

io = StringIO.new(Base64.decode64(encoded_img))
io.original_filename = "foobar.png"

p.image_file = io
p.save

在 Rails 3 中，您需要创建一个新类，然后手动添加original_filename回来

class FilelessIO < StringIO
    attr_accessor :original_filename
end

io = FilelessIO.new(Base64.decode64(encoded_img))
io.original_filename = "foobar.png"

p.image_file = io
p.save
于 2011-07-16T19:09:07.487 回答
1

您不必对 StringIO 进行monkeypatch 或将其中的任何内容放入您的模型中。您可以在上传器定义中覆盖 cache!() 方法。或者你可以更进一步，为自己制作一个模块。我的文件是来自 json 文档的序列化字符串。传入的对象看起来像这样 { :filename => 'something.jpg', :filedata => base64 string }。

这是我的模块：

module CarrierWave
  module Uploader
    module BackboneLink  
      def cache!(new_file=sanitized_file)
        #if new_file isn't what we expect just jump to super
        if new_file.kind_of? Hash and new_file.has_key? :filedata
          #this is from a browser, so it has all that 'data:..' junk to cut off.
          content_type, encoding, string = new_file[:filedata].split(/[:;,]/)[1..3]
          sanitized = CarrierWave::SanitizedFile.new( 
            :tempfile => StringIO.new(Base64.decode64(string)), 
            :filename => new_file[:filename], 
            :content_type => content_type 
          )
          super sanitized
        else
          super
        end
      end
    end
  end
end

然后我可以将它包含在上传器中。上传者/some_uploader.rb：

class SomeUploader < CarrierWave::Uploader::Base

  include CarrierWave::Uploader::BackboneLink
于 2013-09-13T16:27:33.653 回答
0 
class AppSpecificStringIO < StringIO
  attr_accessor :filepath

  def initialize(*args)
    super(*args[1..-1])
    @filepath = args[0]
  end

  def original_filename
    File.basename(filepath)
  end
end

另请参阅carrierwave wiki https://github.com/carrierwaveuploader/carrierwave/wiki/How-to%3A-Upload-from-a-string-in-Rails-3

于 2013-07-03T15:01:18.220 回答