Carrierwave & Zipfiles: Using an extracted file as a version - ruby-on-rails

Question

Something I'm not getting about the version process...
I have a zip file with a file inside, and I want to upload the file as a "version" of the zip:
Uploader:
version :specificFile do
process :extract_file
end
def extract_file
file = nil
Zip::ZipFile.open(current_path) do |zip_file|
file = zip_file.select{|f| f.name.match(/specificFile/)}.first
zip_file.extract(file, "tmp/" + file.name.gsub("/", "-")){ true }
end
File.open("tmp/" + file.name.gsub("/", "-"))
end
Usage:
=link_to "Specific File", instance.uploader.specificFile.url
Only this just nets me two copies of the zip. Clearly, there's something I'm missing about how version / process works, and I haven't been able to find documentation that actually explains the magic.
So how do I do this, and what am I missing?

Answer 1

This provided the "why", although it took a bit to understand:
How do you create a new file in a CarrierWave process?
To rephrase, when you go to create a version, carrierwave makes a copy of the file and then passes the process the file path. When the process exits, carrierwave will upload the contents of that path - not the file the process returns, which is what I thought was going on.
Working code:
version :specificFile do
process :extract_file
def full_filename (for_file = model.logo.file)
"SpecificFile.ext"
end
end
def extract_plist
file = nil
Zip::ZipFile.open(current_path) do |zip_file|
file = zip_file.select{|f| f.name.match(/specificFile/)}.first
zip_file.extract(file, "tmp/" + file.name.gsub("/", "-")){ true }
end
File.delete(current_path)
FileUtils.cp("tmp/" + file.name.gsub("/", "-"), current_path)
end
So, to make what I want to happen, happen, I:
Tell carrierwave to use a particular filename. I'm using a hardcoded value but you should be able to use whatever you want.
Overwrite the contents of current_path with the contents you want under the version name. In my case, I can't just overwrite the zip while I'm "in it" (I think), so I make a copy of the file I care about and overwrite the zip via File and FileUtils.
PS - It would be nice to avoid the duplication of the zip, but it doesn't look like you can tell carrierwave to skip the duplication.