Generate unique filename

Question

I need unique filenames for my files.

def filename
    "#{SecureRandom.urlsafe_base64}.gif"
end

This saves a file such as this:

ylGP48WxZXOY2OQ_x9dxAA.gif

however its respective field in the database to be saved like this:

jED48PRNz0asZzwYQXzecw.gif

I think what's happening is that Carrierwave is calling the file_name function when it's writing the file and when its saving the instance in the database, resulting in urlsafe_base64 being called twice and creating two different strings. It works perfectly when I've hardcoded a name as a test.

So how can stop this? I know it's outrageous to ask, but how can I make Carrierwave use the same randomly generated filename in the database and when writing the file? I seriously think this should be considered a bug.

Answer 1

This is one option:

  def filename
    random_string
  end   

  protected 

  def random_string
    @string ||= "#{SecureRandom.urlsafe_base64}.gif"
  end

I agree carrierwave could a be a tad more intuitive.

Answer 2

http://ruby-doc.org/stdlib-2.4.0/libdoc/tempfile/rdoc/Tempfile.html

Tempfile

A utility class for managing temporary files. When you create a Tempfile object, it will create a temporary file with a unique filename. A Tempfile objects behaves just like a File object, and you can perform all the usual file operations on it: reading data, writing data, changing its permissions, etc. So although this class does not explicitly document all instance methods supported by File, you can in fact call any File instance method on a Tempfile object.

require 'tempfile'

file = Tempfile.new('foo')
file.path      # => A unique filename in the OS's temp directory,
               #    e.g.: "/tmp/foo.24722.0"
               #    This filename contains 'foo' in its basename.
file.write("hello world")
file.rewind
file.read      # => "hello world"
file.close
file.unlink    # deletes the temp file