class ActionView::Helpers::Tags::Select

:nodoc:
:nodoc:

def grouped_choices?

{ nil => [] }
[nil, []]

Grouped choices look like this: 
def grouped_choices?
  !@choices.empty? && @choices.first.respond_to?(:last) && Array === @choices.first.last
end

def initialize(object_name, method_name, template_object, choices, options, html_options)

:nodoc:
:nodoc: 
def initialize(object_name, method_name, template_object, choices, options, html_options)
  @choices = block_given? ? template_object.capture { yield } : choices
  @choices = @choices.to_a if @choices.is_a?(Range)
  @html_options = html_options
  super(object_name, method_name, template_object, options)
end

def render 

def render
  option_tags_options = {
    :selected => @options.fetch(:selected) { value(@object) },
    :disabled => @options[:disabled]
  }
  option_tags = if grouped_choices?
    grouped_options_for_select(@choices, option_tags_options)
  else
    options_for_select(@choices, option_tags_options)
  end
  select_content_tag(option_tags, @options, @html_options)
end