How do I duplicate a file stored in ActiveStorage in Rails 5.2

Question

I have a model that is using ActiveStorage:

class Package < ApplicationRecord
  has_one_attached :poster_image
end

How do I create a copy of a Package object that contains a duplicate of the initial poster_image file. Something along the lines of:

original = Package.first
copy = original.dup
copy.poster_image.attach = original.poster_image.copy_of_file

Answer 1

Update your model:

class Package < ApplicationRecord
  has_one_attached :poster_image
end

Attach the source package’s poster image blob to the destination package:

source_package.dup.tap do |destination_package|
  destination_package.poster_image.attach(source_package.poster_image.blob)
end

Answer 2

If you want a full copy of the file so that both the original record and the cloned record have their own copy of the attached file, do this:

In Rails 5.2, grab this code and put it in config/initializers/active_storage.rb, then use this code to do a copy:

ActiveStorage::Downloader.new(original.poster_image).download_blob_to_tempfile do |tempfile|
  copy.poster_image.attach({
    io: tempfile, 
    filename: original.poster_image.blob.filename, 
    content_type: original.poster_image.blob.content_type 
  })
end

After Rails 5.2 (whenever a release includes this commit), then you can just do this:

original.poster_image.blob.open do |tempfile|
  copy.poster_image.attach({
    io: tempfile, 
    filename: original.poster_image.blob.filename, 
    content_type: original.poster_image.blob.content_type 
  })
end

Thanks, George, for your original answer and for your Rails contributions. :)

Answer 3

Found the answer by looking through Rails's tests, specifically in the blob model test

So for this case

class Package < ApplicationRecord
  has_one_attached :poster_image
end

You can duplicate the attachment as such

original = Package.first
copy = original.dup
copy.poster_image.attach \
  :io           => StringIO.new(original.poster_image.download),
  :filename     => original.poster_image.filename,
  :content_type => original.poster_image.content_type

The same approach works with has_many_attachments

class Post < ApplicationRecord
  has_many_attached :images
end

original = Post.first
copy = original.dup

original.images.each do |image|
  copy.images.attach \
    :io           => StringIO.new(image.download),
    :filename     => image.filename,
    :content_type => image.content_type
end

Answer 4

It worked for me:

copy.poster_image.attach(original.poster_image.blob)