Rails generate select with both options and option groups - ruby-on-rails

Question

Is it possible to generate select like:
<select>
<option value>Some nill value label</option>
<option value="1">Option one</option>
<optgroup label="Option Group 1" class="css-class-for-option-group-1">
<option value="1:1">Option one in group 1</option>
<option value="1:2">Option two in group 1</option>
</optgroup>
<optgroup label="Option Group 2" class="css-class-for-option-group-2">
<option value="2:1">Option one in group 2</option>
<option value="2:2">Option two in group 2</option>
</optgroup>
</select>
I tried to use the grouped_options_for_select, but I failed to find I way to pass both option and groups to it. Is there any way to achieve this? I am open to suggestions using SimpleForm as well.
Thanks!

Answer 1

This is hard to answer precisely without knowing what the data looks like, but I'm going to guess that you have something like this:
#grouped_options = [
["Some nil value label"],
["Option one", "1"],
["Option Group 1",
[
["Option one in group 1", "1:1"],
["Option two in group 1", "1:2"],
]
],
["Option Group 2",
[
["Option one in group 2", "2:1"],
["Option two in group 2", "2:2"],
]
],
]
With that, you have a couple options. In plain ERB, you can do it like this:
<%= select "thing", "some_attr" do %>
<% #grouped_options.each do |label, value_or_options| %>
<% if Array === value_or_options %>
<%= tag.optgroup options_for_select(value_or_options), label: label %>
<% else %>
<%= tag.option label, value: value_or_options %>
<% end %>
<% end %>
<% end %>
Personally, though, I would write a helper. The Enumerable#chunk method splits an array into runs of values that return the same thing for the given block, making it easy to separate the grouped from the non-grouped items so we can use grouped_options_for_select and options_for_select, respectively:
def ungrouped_and_grouped_options_for_select(choices, selected_key = nil)
capture do
choices
.chunk {|_, choice_or_group| Array === choice_or_group }
.each do |is_group, choices_or_grouped_choices|
if is_group
concat grouped_options_for_select(choices_or_grouped_choices, selected_key)
else
concat options_for_select(choices_or_grouped_choices, selected_key)
end
end
end
end
You could then use it this:
<%= select "thing", "some_attr" do %>
<%= ungrouped_and_grouped_options_for_select(#grouped_options) %>
<% end %>
You can see both of these approaches in action on repl.it: https://repl.it/#jrunning/UnacceptablePlaintiveServer (see views/tests/index.html.erb, controllers/tests_controller.rb, and helpers/application_helper.rb).

Answer 2

Assuming that the data is formatted as described by Jordan, you could also combine both 'select options' methods (options_for_select and grouped_options_for_select) by summing their return, like so:
<%= f.select :selected_ids, options_for_select([['Option 1', 1]]) + grouped_options_for_select([['Option Group 1', ['group1opt1', 11], ['group1opt2', 12]], ['Option Group 2', ['group2opt1', 21], ['group2opt2', 22]]]), {}, { class: 'class' } %>