Patch for ActionView::Helpers to add 'include_selected' option to CollectionSelect, options_from_collection_for_select, options_for_select

include_selected_option.rb

module ActionView::Helpers
    module Tags
      class CollectionSelect < Base
        def render
          option_tags_options = {
              :selected => @options.fetch(:selected) { value(@object) },
              :include_selected => @options.fetch(:include_selected, false),
              :disabled => @options[:disabled]
          }

          select_content_tag(
              options_from_collection_for_select(@collection, @value_method, @text_method, option_tags_options),
              @options, @html_options
          )
        end
      end
    end
    module FormOptionsHelper
      def options_from_collection_for_select(collection, value_method, text_method, selected = nil)
        options = collection.map do |element|
          [value_for_collection(element, text_method), value_for_collection(element, value_method), option_html_attributes(element)]
        end
        selected, disabled, include_selected = extract_selected_and_disabled(selected)
        select_deselect = {
            selected: extract_values_from_collection(collection, value_method, selected),
            disabled: extract_values_from_collection(collection, value_method, disabled),
            include_selected: include_selected
        }

      options_for_select(options, select_deselect)
    end
    def options_for_select(container, selected = nil)
      return container if String === container

      selected, disabled, include_selected = extract_selected_and_disabled(selected)
      selected, disabled = [selected, disabled].map do |r|
        Array(r).map { |item| item.to_s }
      end

      if include_selected
        include = selected.select{|s| container.find{|element| option_text_and_value(element).last == s}.nil?}
        unless include.empty?
          container = [selected] + container
        end
      end

      # Rails 4 version
      container.map do |element|
        html_attributes = option_html_attributes(element)
        text, value = option_text_and_value(element).map(&:to_s)

        html_attributes[:selected] ||= option_value_selected?(value, selected)
        html_attributes[:disabled] ||= disabled && option_value_selected?(value, disabled)
        html_attributes[:value] = value

        content_tag_string(:option, text, html_attributes)
      end.join("\n").html_safe
    end
    def extract_selected_and_disabled(selected)
      if selected.is_a?(Proc)
        [selected, nil, nil]
      else
        selected = Array.wrap(selected)
        options = selected.extract_options!.symbolize_keys
        selected_items = options.fetch(:selected, selected)
        [selected_items, options[:disabled], options[:include_selected]]
      end
    end
  end
end

Rails include_selected

A handy patch for when you want to force-use a select box and not loose any pre-existing/legacy data.

Examples:

language select, with a deprecated language

options_for_select([["English", "en"], ["German", "de"]], {selected: "Russian", include_selected: true})

will result in:

<option value="Russian" selected="selected">Russian<option>
<option value="en">English<option>
<option value="de">German<option>

language select with multiple values

options_for_select([["English", "en"], ["German", "de"]], {selected: ["Russian", "German"], include_selected: true})

will result in:

<option value="Russian" selected="selected">Russian<option>
<option value="en">English<option>
<option value="de" selected="selected">German<option>