How to upload a file temporarily in Rails 3? - ruby

Question

I'm creating CSV-upload functionality for a site of mine.
I'm looking to upload a file, parse it, and then dispose of it.
I know I can upload and save a file using Paperclip, but that seems a bit like overkill.
All I need to do is parse the uploaded file and never save it.
How would I go about doing this in Rails 3?
Note: I'd prefer to do the uploading manually without using an external gem so I can learn how to process works, but any suggestions are welcome.
Thanks!

Answer 1

Use the file_field helper in your form, then in your controller you can use File.Write and File.read to save the file.
E.g. View
<%= form_for #ticket do |f| %>
<%= f.file_field :uploaded_file %>
<% end %>
Controller
def upload
uploaded = params[:ticket][:uploaded_file]
File.open(<insert_filename_here>, 'w') do |file|
file.write(uploaded.read)
end
end
Edit: Just saw #klochner's comment, that link says pretty much what I have said so follow that: RubyOnRails Guides: Uploading Files.

Answer 2

Paste this in your model
def parse_file
File.open(uploaded/file/path, 'w') do |f| # Feed path that user gives in some way
## Parse here
end
end
this in view
<%=form_for #page, :multipart => true do |f|%>
<ul><li><%= f.label :file%></li>
<li><%= f.file_field :uploaded_file%></li></ul>
<%end%>
Let me know if this works. If it fails figure out a way to feed path of uploaded_file in parse_file method (the definite way which will work is storing file location in db and picking up from there, but it is not the right way to do this thing). Otherwise, I guess it should work.

Answer 3

Complete Example
Take, for example, uploading an import file containing contacts. You don't need to store this import file, just process it and discard it.
Routes
routes.rb
resources :contacts do
collection do
get 'import/new', to: :new_import # import_new_contacts_path
post :import, on: :collection # import_contacts_path
end
end
Form
views/contacts/new_import.html.erb
<%= form_for #contacts, url: import_contacts_path, html: { multipart: true } do |f| %>
<%= f.file_field :import_file %>
<% end %>
Controller
controllers/contacts_controller.rb
def new_import
end
def import
begin
Contact.import( params[:contacts][:import_file] )
flash[:success] = "<strong>Contacts Imported!</strong>"
redirect_to contacts_path
rescue => exception
flash[:error] = "There was a problem importing that contacts file.<br>
<strong>#{exception.message}</strong><br>"
redirect_to import_new_contacts_path
end
end
Contact Model
models/contact.rb
def import import_file
File.foreach( import_file.path ).with_index do |line, index|
# Process each line.
# For any errors just raise an error with a message like this:
# raise "There is a duplicate in row #{index + 1}."
# And your controller will redirect the user and show a flash message.
end
end