title: why a dropdown selection passes nil as parameter?
body: <p>i have created a dropdown in my application using the following code:</p>
  
  <pre><code>&lt;% form_for :categories, :url=&gt; {:controller =&gt; 'products', :action =&gt; 'cat'} do |f| %&gt;
  &lt;%= f.select(:category ,  Categories.all.map{ |u| [u.name, u.id] }, :prompt =&gt; "Select a    category") %&gt;
  &lt;input type="submit" value="go"/&gt;
  &lt;%end%&gt;
  </code></pre>
  
  <p>controller:</p>
  
  <pre><code>def cat
   @products = Product.search_category params[:category]
  end
  </code></pre>
  
  <p>it is returning 'nil' as the parameter when i select any category from dropdown. what could be the reason?</p>