deep munge in rails

When submit a form , rails will strip empty params

so you cannot update roles by just clear all roles from this variable.

this is an expected behavior in rails (for security reason)

I also have to try to disable deep_munge but still no luck

# config/application.rb
config.action_dispatch.deep_munge = false

Finally, I try solution below, and it works

= hidden_field_tag('variable[role_ids][]', nil)