Paperclip without Form Upload

I have recently been building a Rails application for which I need to generate a QR code for one of my models that has a URL.  Already using the excellent QREncoder library, I needed to attach the generated PNG to my Rails model.  Being that we are already using Paperclip to manage file attachments, we wanted to utilize the same functionality here.

attr_accessible :qrcode
has_attached_file :qrcode

def after_create
  qr = QREncoder.encode(self.url)
  temp_file =['qr', '.png'], "#{Rails.root.to_s}/tmp/")

    self.qrcode =
    temp_file.unlink # cleanup the temp file...

In the code above, after calling a few Paperclip setup methods, we start by encoding the QR code for the desired URL stored in the model.  We then create a temporary PNG file to which we write the QR code via the QREncoder library (save_png). Paperclip then expects a File be presented to be attached, so we open the temporary file via and save the model. Before we go, we make sure to close and remove (unlink) the temporary file for cleanliness.

Hope this is helpful to others, took a bit of playing.