In Ruby on Rails, grouped collection select returns
From the docs
Example object structure for use with this method:
class Continent < ActiveRecord::Base
has_many :countries
# attribs: id, name
end
class Country < ActiveRecord::Base
belongs_to :continent
# attribs: id, name, continent_id
end
class City < ActiveRecord::Base
belongs_to :country
# attribs: id, name, country_id
end
Sample usage:
grouped_collection_select(:city, :country_id, @continents, :countries, :name, :id, :name)
Possible output:
<select name="city[country_id]">
<optgroup label="Africa">
<option value="1">South Africa</option>
<option value="3">Somalia</option>
</optgroup>
<optgroup label="Europe">
<option value="7" selected="selected">Denmark</option>
<option value="2">Ireland</option>
</optgroup>
</select>
