Rails comes with
grouped_collection_select
Show archive.org snapshot
that appears to be useful, but isn't.
As an alternative, consider the flat_grouped_collection_select found below. It takes a third argument that extracts the group from each element in the collection:
= form.flat_grouped_collection_select :user_id, users, :department, :id, :full_name
Here is the monkey-patch:
class ActionView::Helpers::FormBuilder
def flat_grouped_collection_select(field, collection, group_label_method, value_method, label_method, options = {}, html_options = {})
hash = collection.group_by(&group_label_method).collect_hash do |group_label, group_entries|
list_of_pairs = group_entries.collect { |entry|
[entry.send(label_method), entry.send(value_method).to_s]
}
[group_label, list_of_pairs]
end
options_options = options.slice(:prompt)
selected_key = object.send(field).to_s
select(field, @template.grouped_options_for_select(hash, selected_key, options_options), options, html_options)
end
end
Posted by Henning Koch to makandra dev (2015-06-16 14:07)