Renaming uploaded files with Carrierwave

Question

I\'m using Carrierwave to upload files, and I have it working.

My issue is attempting to change the name of the uploaded file.

In the generated uploader.rb there

Answer 1

To have a real unique filename (not almost unique) I recommend to use the uuid gem.

in Gemfile add:

gem 'uuid'

in file_uploader.rb:

def filename
  if original_filename
    if model && model.read_attribute(mounted_as).present?
      model.read_attribute(mounted_as)
    else
      @name ||= "#{mounted_as}-#{uuid}.#{file.extension}"
    end
  end
end

protected

def uuid
  UUID.state_file = false
  uuid = UUID.new
  uuid.generate
end

Answer 2

To just make the record.id prefix the filename you can do the following:

class MyUploader < CarrierWave::Uploader::Base

  storage :file

  def store_dir
    model.class.to_s.underscore.pluralize
  end

  def filename
    model.id ? "#{model.id}-#{original_filename}" : original_filename
  end

  def url
    "/#{store_dir}/#{model.id}-#{model.file_before_type_cast}"
  end
end

Answer 3

Here is the solution, how to change the name of the file, if store_dir already contains the file with the exact name:

  if File.exists?(Rails.root.join("documents/" + "#{file.filename}")) && !path.to_s.eql?(Rails.root.join("documents/" + original_filename).to_s)
    @name ||= File.basename(original_filename, '.*') + Digest::MD5.hexdigest(File.dirname(current_path)).from(25)
    "#{@name}.#{file.extension}"
  else
    "#{original_filename}"
  end

Note: Rails.root.join("documents/") is defined as my store_dir.

Hope it helps someone.

Answer 4

From the Google Group:

def filename
  @name ||= "#{secure_token}.#{file.extension}" if original_filename
end

private

def secure_token
  ivar = "@#{mounted_as}_secure_token"
  token = model.instance_variable_get(ivar)
  token ||= model.instance_variable_set(ivar, ActiveSupport::SecureRandom.hex(4))  
end

Answer 5

Well, another problem with your random filename generator is that it's possible to have collisions isn't it? You could possibly generate a filename that was already generated. One way to go about it would be to somehow generate a hash based on unique properties of the image, like file path. An example, from the carrierwave group:

def filename 
  if original_filename 
    @name ||= Digest::MD5.hexdigest(File.dirname(current_path))
    "#{@name}.#{file.extension}"
  end
end

This will create an MD5 hash based on the current path and then append the original file's extension to it.

Edit: The carrierwave wiki added an entry with a few methods on how to create random and unique filenames for all versioned files.

Answer 6

The other solution looks good, but how I did it then was to have a hook that created a random string for a new name on instance creation, then:

 def filename
    "#{model.randomstring}.#{model.image.file.extension}"
 end

in the uploader.

That worked, putting the random name generation as part of the model, then having carrierwave use that.

I am curious which is faster, more effective, reasonable, sound, etc.