How can I implement grouped_collection_select for my model which is use closure_tree gem?
I have Location model, which is have name and parent_id attribute. I want to do something like this.
<select name="locations">
  <optgroup label="Office">
    <option value="3">Office Table 1</option>
    <option value="4">Office Table 2</option>
  </optgroup>
  <optgroup label="Lab">
    <option value="5">Another Door 1</option>
    <option value="6">Another Door 2</option>
    <option value="7">Another Door 3</option>
    <option value="8">Another Door 4</option>
    <option value="11">Another Door 5</option>
  </optgroup>
  ⋮
</select>