<%= form_for(@plan) do |f| %> <% f.fields_for :meals do |meal| %> <%= meal.fields_for :meal_portions do |mp| %>

<%= mp.fields_for :substitutes do |sub| %> <%= render "plans/meals/substitutes_fields", obj: sub, mp: mp %> <% end %>

<% end %> <% end %> <% end %>