Question

Looking at the example of form_for from the rails docs, I see this example:

<%= form_for @person do |person_form| %>
  First name: <%= person_form.text_field :first_name %>
  Last name : <%= person_form.text_field :last_name %>

  <%= fields_for @person.permission do |permission_fields| %>
    Admin?  : <%= permission_fields.check_box :admin %>
  <% end %>

  <%= f.submit %>
<% end %>

I tried copying this template, but noticed that in order to get the update to work correctly, I had to change the field_for line to

 <%= person_form.fields_for @person.permission do |permission_fields| %>

Any idea why they are showing the fields_for without the parent form variable in front (person_form)?

The examples later in the docs show it with the parent form variable.

Thanks

Answer 1

it is correct with person_form. think of it as the formtag and you just assign the inputs to the form. all the names of the form get set like this (person[attribute]). fields_for without person_form would create other name like (permission[admin]) – this would fail because the permission object is not connected with the person. through the person_form.fields_for the names get right (person[permission][admin]). you get the nested attribute without doing anything more.