Rails Import CSV - All Values 'Nil' - ruby-on-rails

Question

I'm learning how to import csv to a rails application. However, when i run the application, all the values turned out to be 'nil'. May I know what is wrong with my codes below?
Controller
def import_csv
#list = List.find(params[:list_id])
#lists = List.all
respond_to do |format|
#csv=params[:file]
#n=0
CSV.parse(#csv).each do | row |
#user_new = User.new
#user_new.first_name = row[0]
#user_new.last_name = row[1]
#user_new.email = row[2]
#user_new.address = row[3]
#user_new.city = row[4]
#user_new.state = row[5]
#user_new.zipcode = row[6]
#user_new.country = row[7]
#user_new.notes = row[8]
#user_new.birthday = row[9]
#user_new.home_number = row[10]
#user_new.mobile_number = row[11]
#user_new.list_id = #list.id
#user_new.save
#n=#n+1
GC.start if #n%50==0
flash[:notice] = "CSV Imported Successfully, with #{#n} records"
end
format.html { redirect_to lists_url }
format.json { head :no_content }
end
end
View
<%= form_for(:list, :url => list_import_csv_path(#list), :method => :get, :html => {:multipart => true}) do |f| %>
<table>
<tr>
<td><label for="dump_file">Select a CSV File :</label></td>
<td ><%= file_field_tag :file %></td>
</tr>
<tr>
<td colspan='2'><%= submit_tag 'Submit' %></td>
</tr>
</table>
<% end %>

Answer 1

I think you got problems on you form sending it in the url try something like this. (I got a custom action on my controller called import)
<%= form_tag #list, :action => 'import', :multipart => true do |f| %>
<label class="control-label" for="fileInput" style="width: 160px">Select file: </label>
<%= file_field_tag 'file', :accept => 'text/html', :size => 60%>
<div class="form-actions">
<%= submit_tag 'SUbmit', :class=>"btn" %>
</div>
<% end %>
Try to follow this tutorial it has an excellent example of importing and exporting.Check it out