File upload to box.com without writing to file system - ruby-on-rails

Question

I am trying to upload a file to Box.com using its API REST call and the httmultiparty gem. The code is working and uploads to Box.com but does that after writing the uploaded file to the server file system as in f.write(data.read) then capturing the file path for the written file as the input parameter to the Box.com API REST call as in :filename => File.new(path). The app will be running on Heroku, so we can't save any files (read only) on Heroku's server so I would like to directly upload the file to Box.com while bypassing the writing of the file on the server but can't figure that out given that the Box.com REST call requires an object of type "File". Any help is appreciated. Thanks.
The model and view code is:
###
#The Model
###
class BoxUploader
require 'httmultiparty'
include HTTMultiParty
#base_uri 'https://api.box.com/2.0'
end
class File < ActiveRecord::Base
attr_accessible :file
attr_accessor :boxResponse
FILE_STORE = File.join Rails.root, 'public', 'files'
API_KEY = #myBoxApiKey
AUTH_TOKEN = #myBoxAuthToken
def file=(data) #uploaded file
filename = data.original_filename
path = File.join FILE_STORE, filename
#### would like to bypass the file writing step
File.open(path, "wb") do |f|
f.write(data.read)
end
#############
File.open(path, "wb") do |f|
boxResponse = BoxUploader.post('https://api.box.com/2.0/files/content',
:headers => { 'authorization' => 'BoxAuth api_key={API_KEY&auth_token=AUTH_TOKEN' },
:body => { :folder_id => '911', :filename => File.new(path)}
)
end
end
###
# The View
###
<!-- Invoke the Controller's "create" action -->
<h1>File Upload</h1>
<%= form_for #file, :html => {:multipart=>true} do |f| %>
<p>
<%= f.label :file %>
<%= f.file_field :file %>
</p>
<p>
<%= f.submit 'Create' %>
<% end %>

Answer 1

To upload a file from memory with HTTMultiParty, you need to supply it with an UploadIO object in place of the File object you'd normally give it. The UploadIO object can be populated using StringIO. It seems HTTMultiParty handles UploadIO objects in a special way, so you can't use the StringIO directly:
class Uploader
include HTTMultiParty
base_uri "http://foo.com"
end
string_io = StringIO.new('some stuff that pretends to be in a file')
upload_io = UploadIO.new(string_io, 'text/plain', 'bar.txt')
Uploader.post("/some/path", query: {file: upload_io})

Answer 2

You are aiming at a non-common use pattern, so your best shot could be to extend the existant gem, to provide the functionality you need.
There is a gem ruby-box to use with Box service at the 2.0 version of their API.
The gem is well supported and pretty easy to use.
You'll need to dig on the source code and create a new upload method.