How to calculate in nested form

rubyonrails-talk
1

Hello i want to calculate between two fields in a nested form.
like Invoice and invoice item.
invoice item have many item, and each item have name, quantity, price and total.
total of that will be quantity * price.

this is the form

<%= form.fields_for :expenseitems do |builder| %>
   <%= render  "expenseitem", form: builder %>
<% end %>

and this is the partial.

<tr>
  <td class="col-6">
    <small>
      <%= form.text_field :itemname, class: 'form-control form-control-sm', placeholder: 'Item Name' %>
    </small>
  </td>
  <td>
    <%= form.text_field :itemqty, class: 'form-control itemqty', placeholder: 'Item QTY' %>
  </td>
  <td>
    <%= form.text_field :itemprice, class: 'form-control itemprice', placeholder: 'Item Price' %>
  </td>
  <td>
    <%# Total price for each item%>
    <%= form.text_field :itemtotal, class: 'form-control  itemtotal', disabled: 'disabled'%>
  </td>
  <td>
    <%= form.hidden_field :_destroy, as: :hidden %>
    <%= link_to "#", class: 'btn btn-sm btn-danger text-xs remove-fields' do %>
    Delete
    <% end %>
  </td>
</tr>

i want to total of each item. how can i do this?

thank you

2

Do you want to calculate it on the server before the form is rendered or In the browser while the user is typing?

1 Like
3

Thank you for your replay. I want to save that on server, after press update or save. Thank you

4

This means that in the controller you know both values so in the controller you can sum them up

def update
   object.update(object_params)
   object.expressitems....# sum and produce the total
end
5

You will have to use javascript and set the value to a hidden field - that way you can avoid server-side calculation