https://github.com/elabs/refile
Refile is a modern file upload library for Ruby applications. It is simple, yet powerful.
Features:
- Configurable backends, file system, S3, etc...
- Convenient integration with ORMs
- On the fly manipulation of images and other files
- Streaming IO for fast and memory friendly uploads
- Works across form redisplays, i.e. when validations fail, even on S3
- Effortless direct uploads, even to S3
楼主少发了一个十分重要的信息 
Refile is a modern file upload library for Ruby applications. It is simple, yet powerful. Refile is an attempt by CarrierWave's original author to fix the design mistakes and overengineering in CarrierWave.
