formtastic check_boxes using collection not saving checked items in edit form

问题

I know this was supposed to be fixed in Formtastic 2.0 but for some reason, this isn't working for me.

          <%= f.input :gender, :as => :check_boxes, :collection => ["Male", "Female", "Unisex"] %>      

Whenever I go back and check it, the items is always unchecked again. It never appears as selected. I know Justin French commented about it here, but I am not sure what it means or how that can help me fix the problem.

I am saving gender as a string in the User model if it makes a difference.

I am also using it with formtastic-bootstrap 1.1.1

Thank you!

来源：https://stackoverflow.com/questions/9727890/formtastic-check-boxes-using-collection-not-saving-checked-items-in-edit-form