<% if notice %>
<p id="notice"><%= notice %></p>
<% end %>
<h2>Your Pragmatic Cart</h2>
<ul>
<% @cart.line_items.each do |item| %>
<li><%= item.quantity %> × <%= item.product.title %></li>
<% end %>
</ul>
<%= button_to 'Empty cart', @cart, method: :delete, confirm: 'Are you sure?' %>
<%= button_to 'Empty cart', @cart, method: :delete, confirm: 'Are you sure?' %> 这行代码里的@cart表示的是什么?我看官方文档是 button_to(name = nil, options = nil, html_options = nil, &block),还是不大明白。求解释?