tap/app/views/products/new.html.erb

<%= form_for @product, html: { multipart: true } do |f| %>
  <%= render 'application/errors', model: @product %>

  <%= f.label :name %>
  <%= f.text_field :name %>

  <%= f.label :purchase_price %>
  <%= f.number_field :purchase_price %>

  <%= f.label :sale_price %>
  <%= f.number_field :sale_price %>

  <%= f.label :avatar %>
  <%= f.file_field :avatar %>

  <%= f.submit "Create product", class: "btn btn-primary" %>
<% end %>