Cannot have both select and radio_button together on the same form

Hello, I'm new to Ruby on Rails.

I am creating a form for searching purpose:

<% form_for :src_cond,       :url => {:action =>'search'} do |p| %>      <%= p.radio_button("bd", "1") %> a      <%= p.radio_button("bd", "2") %> b      <%= p.select :bd2, %w[1 2 3 4],{},{:index=>nil} %>      <%= p.submit "Search" %> <% end %>

When I click "Search", the browser shows:

"We're sorry, but something went wrong. We've been notified about this issue and we'll take a look at it shortly."

When I check the log, it says:

  Status: 500 Internal Server Error   expected Array (got Hash) for param `src_cond'

I've put some "puts" statements in the controller, which indicates the controller is not called at all.

If I have only radio_button or select in the form, the controller will be called as expected.

I wonder how I may have both combo box and radio group at the same time.

Many thanks!!

What are you trying to achieve with {:index=>nil} on the select helper? <%= p.select :bd2, %w[1 2 3 4] %> should work