rails upload attachment (contact form)

contact.html.erb

<h1>Contact</h1>


<%= form_tag("/send_to", :method=>'post', :multipart => true) do %>
 <p>
   Subject:<br />
   <%= text_field_tag "subject"  %>
 </p>
 <p>
   Priority: <br />
   <%= select_tag("priority", options_for_select([['Critical', '1'],
                 ['Important', '2'],['Standard','3']], '3')) %>
 </p>
 <p>
   Describe your problem:<br />
   <%= text_area_tag "description", "", :size=>"10x10" %>
 </p>
 <p>
   Add an attachment:<br />
   <%= file_field_tag "attachment" %>
 </p>
 <p>
   <%= submit_tag 'Submit', :class => 'btn btn-primary' %>
 </p>
<% end %>

do_contact.html.erb

New Message!

<%=@description%>

staticsController.rb

class StaticsController < ApplicationController

  def contact
  
    
  end
  
  
  def send_to
    
    subject = params[:subject]
    description = params[:description]
    attachment = params[:attachment]

    Testmailer.do_contact(subject,description,attachment).deliver
    flash[:notice] = "email sent"
    redirect_to :back
  end
end

testmailer.rb

class Testmailer < ActionMailer::Base
  default :from => "xxx@gmail.com"
  
  def do_contact(subject,description,attachment)
    @description =description 
    
    if attachment
    attachments[attachment.original_filename] = File.open(attachment.path, 'rb'){|f| f.read}
    end
    
    mail(:to => "xxx@gmail.com", :subject => subject)
  end
end