resources :categories do
  resources :products
end

根据Rails Guides,

You can also use url_for with a set of objects,and Rails will automatically determine which route you want:

06001

In this case,Rails will see that @magazine is a Magazine and @ad is an Ad and will therefore use the magazine_ad_path helper. In helpers like link_to,you can specify just the object in place of the full url_for call:

06002

For other actions,you just need to insert the action name as the first element of the array:

06003

就我而言,我有以下代码,它们功能齐全：

<% @products.each do |product| %>
  <tr>
    <td><%= product.name %></td>
    <td><%= link_to 'Show',category_product_path(product,category_id: product.category_id) %></td>
    <td><%= link_to 'Edit',edit_category_product_path(product,category_id: product.category_id) %></td>
    <td><%= link_to 'Destroy',category_id: product.category_id),method: :delete,data: { confirm: 'Are you sure?' } %></td>
  </tr>
<% end %>

显然它有点太冗长了,我想用rails guide中提到的技巧来缩短它.

但是,如果我更改了显示和编辑链接,如下所示：

<% @products.each do |product| %>
  <tr>
    <td><%= product.name %></td>
    <td><%= link_to 'Show',[product,product.category_id] %></td>
    <td><%= link_to 'Edit',[:edit,product,product.category_id] %></td>
    <td><%= link_to 'Destroy',data: { confirm: 'Are you sure?' } %></td>
  </tr>
<% end %>

它们都不再起作用了,页面抱怨同样的事情：

NoMethodError in Products#index
Showing /root/Projects/foo/app/views/products/index.html.erb where line #16 raised:

undefined method `persisted?' for 3:Fixnum

我错过了什么？