How to reference form field values after a page reload to preserve input values?

Question

I have the following simple_form_for with date selectors to filter Invoices by due date.

When the user inputs a start_date and end_date and submits to filter the invoices, the page reloads and the form fields are reset (the "pick a date" placeholder shows).

How can I reference those field's values so when the page reloads their values are the ones previously selected? (they are in the params now).

I tried adding a value: f.object.start_date option but it doesn't seem to work.

I also tried value: params[:date_params][:start_date] to no success either.

  <div class="col-md-6 my-2" >
    <%= simple_form_for :date_params, { url: admin_invoices_batch_edit_index_path, method: :get } do |f| %>
      <%= f.input :start_date, as: :string, placeholder: "Pick a start date",
                  input_html: { data:{ controller: "flatpickr",
                  attributes:{ enableTime: false, enableSeconds: false } } } %>

      <%= f.input :end_date, as: :string, placeholder: "Pick an end date",
                  input_html: { data:{ controller: "flatpickr",
                  attributes:{ enableTime: false, enableSeconds: false } } } %>
      <%= f.button :submit, "Filter" %>
    <% end %>
  </div>

Answer 1

In your controller action, grab the parameter values.

@start_date = params.has_key?(:date_params) ? params[:date_params][:start_date] : nil
@end_date = params.has_key?(:date_params) ? params[:date_params][:end_date] : nil

In your view add the value to the input_html for each param

input_html: { value: @start_date ...

This will set the parameters when available or leave them as nil when not.