polymorphic_select_tag

gistfile1.rb

# polymorphic_select_tag @item, :owner, Post.all(:order=>'created_at DESC').collect{|b| #[b.title, [Post, b.id]]} 

  def polymorphic_select_tag(object, field, option_array=[], options={}, html_options={})
    option_tags = "<option #{'selected="selected"' if (object.try(field) == nil)}/>" +
      option_array.map do |tuple|
        "<option value='#{tuple[1][0]}-#{tuple[1][1]}' #{'selected="selected"' if ((object.try(field).try(:id).to_s == tuple[1][1].to_s && object.try(field).try(:type).to_s == tuple[1][0].to_s) rescue false)}>#{tuple[0]}</option>"
      end.to_s

    prefix               = options[:prefix] || ''
    object_id            = object.id
    object_type          = object.class.name.downcase
    select_tag_id        = "__#{prefix}_#{object_type}_#{field}_select_#{object_id}__"
    hidden_type_field_id = "#{prefix}_#{object_type}_#{field}_type_#{object_id}"
    hidden_id_field_id   = "#{prefix}_#{object_type}_#{field}_id_#{object_id}"

    onchange = "$('##{hidden_id_field_id}').val($('##{select_tag_id}').val().split('-')[1]);"+
               "$('##{hidden_type_field_id}').val($('##{select_tag_id}').val().split('-')[0]);"

    hidden_field_tag("#{object_type}[#{field}_type]", object.try(field).try(:type).to_s, :id => hidden_type_field_id) +
    hidden_field_tag("#{object_type}[#{field}_id]", object.try(field).try(:id).to_s,   :id => hidden_id_field_id) +
    select_tag(select_tag_id, option_tags, 
               html_options.merge(:onchange => onchange))
  end