Stimulus Reflex populate dropdowns

region_reflex.rb

class RegionReflex < ApplicationReflex
  def select_state
    state_id = element[:value].to_i
    @state = State.find(state_id)
    @state_cities = @state&.cities
  end
end

state_select.html.erb

<%= form_with model... %>

  <div class="mt-6">
    <%= form.label :state_id, class: "block text-sm font-medium text-gray-700" %>
    <%# Here I add the data: {reflex: "change->Region#select_state"} - so for every new selection the reflex is triggered. %>
    <%= form.collection_select(:state_id, State.all.order(name: :asc), :id, :name, { prompt: true }, data: {reflex: "change->Region#select_state"}, class: "drop-down") %>
  </div>

  <div>
    <p>Select a city...</p>
    <%# the variable @state_cities is then available from the reflex %>
    <%= form.collection_select(:host_id, @state_cities.order(first_name: :asc), :id, :name, { prompt: true },  class: "drop-down") %>
  </div>
  
  <div>
    <%= form.submit %>
  </div

<% end %>