Renaming uploaded files with Carrierwave - ruby-on-rails

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 is a method I think I should be using
def filename
"something.jpg" if original_filename
basename = "what"+orginal_filename if original_filename, works
basename = (0...8).map{65.+(rand(25)).chr}.join if original_filename # will create a random name for each version, e.g. the orginal, the thumb, and the filename in the db, useless
end
I can't seem to access items like 'extension' or 'content_type' in sanitized_file.rb, so this is a bit beyond my current skill level right now.
Any suggestions or exercises for doing this, i.e. generate filename for an uploaded file that works as well as the carrierwave default (do nothing, but does carry on to each version)? Seems like it should be simple enough but I've stumbled over this.

Answer 1

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 2

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 3

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 4

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 5

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.

Answer 6

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.