<%= form_tag({:action => :upload}, :multipart => true) do %>
<%= file_field_tag 'picture' %>
<% end %>
<%= form_for @person do |f| %>
<%= f.file_field :picture %>
<% end %>
def upload
uploaded_io = params[:person][:picture]
File.open(Rails.root.join('public', 'uploads', uploaded_io.original_filename), 'w') do |file|
file.write(uploaded_io.read)
end
end