tekin

<%= options_from_collection_for_select(
  @products,
  :id,
  :name,
  nil,                       # selected value(s)
  lambda{|p| !p.in_stock? }  # disabled value(s) identified with a proc 
) %>

tekin

<%= options_for_select(
  ['Choose a size', 'small', 'medium', 'large'],
  nil,     # selected value
  'medium' # disabled value
) %>

<!-- Gives you -->

<option value="Choose a size">Please choose a size</option>
<option value="s">small</option>

tekin

<%= options_from_collection_for_select(@product.sizes, :name, :id, :disabled => lambda{|size| size.out_of_stock?}) %>

<!-- If small and medium returned true for the method out_of_stock?, you’d get something like: -->

<option value=“23“ disabled=“disabled“>small</option>
<option value=“24“ disabled=“disabled“>medium</option>
<option value=“25“>large</option>
<option value=“26“>extra large</option>

tekin

<%= select(:post, :category, Post::CATEGORIES, :disabled => 'private') %>

<!— Give's you something like —> 

<select name="post[category]">
	<option>story</option>
	<option>joke</option>
	<option>poem</option>
	<option disabled="disabled">private</option>
</select>