Paperclip Custom Interpolations
As web developers something we often have to implement is handling file uploads. With Rails there are a number of plugins and gems for helping with this. The one I use most often is Paperclip. Out of the box, Paperclip does exactly what you want, and you don’t have to think about any configuration. But, as your application matures, your needs often change and some custom configuration is often required. One thing you’ll notice is that you can customize where the file is stored. The way that you do this (for those new to Paperclip) is:
has_attached_file :asset, :url => "/system/uploads/:class/:attachment/:id/:basename_:style.:extension"
On a recent project the client wanted us to store uploads in a very specific path structure. On the surface this seemed a simple enough request. As we dug deeper, though, it became clear that one part of the path needed to be based on the attribute of a model that was related to the model on which the file data was being stored. By default Paperclip only allows a limited set of values to be used in the path: filename, timestamp, rails_env, class, basename, extension, id, fingerprint, id_partition, attachment, and style. These predefined interpolations are all you need most of the time, but our case was the exception.