Rails setting form action route dynamically via collection select

Ruby on Rails
1

I’ve got a polymorphic association for group_invitations. You can invite users to join product as a member or to join product_customer (it’s not user, it’s something like product customer case) as a customer. To be able to join they have to accept the invitation.

Since it’s polymorphic I decided to do the create action with more controllers instead of using hidden fields. Thanks to that route actions look like:

products/1/group_invitations
product_customers/1/group_invitations

My problem is that I render all the forms on the product show page. So it’s easy to render the form for the certain product like:

<%= form_for([@product, GroupInvitation.new]) do %>
..........

But I’m stuck with the product_customer. Since product has_many product_customers (again it’s not the user but the “product customer case”), user should choose the product_customer instance with collection select and rails should set the form action route based on that. How can I achieve that? Is there a rails way to set it somehow or I gotta use js/jquery?

<%= form_for( #should be set based on collection select ) do %>

  <%= f.collection_select(:product_customer_id, @product.product_customers, :id, :name) %>

TL;DR Rest of the code is provided just to show how controllers/routes look like. According to me not necessary to solve the problem.

routes.rb

resources :group_invitations, only: :destroy do
  member do
    patch :accept
  end
end

resources :products do
  resources :group_invitations, only: [:new, :create], module: :products
end

resources :product_customers do
  resources :group_invitations, only: [:new, :create], module: :product_customers
end

products/group_invitations_controller

class Products::GroupInvitationsController < GroupInvitationsController
  before_action :set_group_invitable

  private

    def set_group_invitable
      @group_invitable = Product.find(params[:product_id])
    end
end

product_customers/group_invitations_controller

class ProductCustomers::GroupInvitationsController < GroupInvitationsController
  before_action :set_group_invitable

  private

    def set_group_invitable
      @group_invitable = ProductCustomer.find(params[:product_customer_id])
    end
end

controllers/group_invitations_controller.rb

def create
  @product = Product.find(params[:product_id])
  @group_invitation = @group_invitable.group_invitations.new(group_invitations_params)
  @group_invitation.sender = @product.owner
  @group_invitation.recipient = @recipient
  if @group_invitation.save
    .........
2

I could solve it with jQuery, but not sure if that’s the best approach.

$(document).on('change', '#product-customer-collection-select', function () {
  var newRouteId = $(this).val();
  var newActionURL = "/product_customers/" + newRouteId + "/group_invitations";
  $(this).closest("form").attr("action", newActionURL);
});