我有个很简单的需求，一个大的 form 里面嵌套着个小 form，而小 form 是 ajax 请求 (remote= true)。

试着用 form_tag 写了下，发现生成的 HTML 里面嵌套在里面的小 form 出不来，

<%= form_tag("/search", method: "get") do %>
  <%= label_tag(:q, "Search for:") %>
  <%= text_field_tag(:q) %>
  <%= submit_tag("Search") %>

  <%= form_tag("/searchapp", method: "get", remote:true) do %>
    <%= label_tag(:q, "Search for:") %>
    <%= text_field_tag(:q) %>
    <%= submit_tag("Search") %>
  <% end %>

<% end %>

生成的 html

<form method="get" action="/search" accept-charset="UTF-8"><div style="margin:0;padding:0;display:inline"><input type="hidden" value="✓" name="utf8"></div>
  <label for="q">Search for:</label>
  <input type="text" name="q" id="q">
  <input type="submit" value="Search" name="commit">

  <div style="margin:0;padding:0;display:inline"><input type="hidden" value="✓" name="utf8"></div>
    <label for="q">Search for:</label>
    <input type="text" name="q" id="q">
    <input type="submit" value="Search" name="commit">
</form>

如果改成嵌套 2 个 form 的话，第二个 form 却出来了，但不是在大 form 里面

<%= form_tag("/search", method: "get") do %>
  <%= label_tag(:q, "Search for:") %>
  <%= text_field_tag(:q) %>
  <%= submit_tag("Search") %>

  <%= form_tag("/searchapp", method: "get", remote:true) do %>
    <%= label_tag(:q, "Search for:") %>
    <%= text_field_tag(:q) %>
    <%= submit_tag("Search") %>
  <% end %>

  <%= form_tag("/searchapp2", method: "get", remote:true) do %>
    <%= label_tag(:q, "Search for:") %>
    <%= text_field_tag(:q) %>
    <%= submit_tag("Search") %>
  <% end %>
<% end %>

生成的 html 如下

<form method="get" action="/search" accept-charset="UTF-8"><div style="margin:0;padding:0;display:inline"><input type="hidden" value="✓" name="utf8"></div>
  <label for="q">Search for:</label>
  <input type="text" name="q" id="q">
  <input type="submit" value="Search" name="commit">

  <div style="margin:0;padding:0;display:inline"><input type="hidden" value="✓" name="utf8"></div>
    <label for="q">Search for:</label>
    <input type="text" name="q" id="q">
    <input type="submit" value="Search" name="commit">
</form>

<form method="get" data-remote="true" action="/searchapp2" accept-charset="UTF-8"><div style="margin:0;padding:0;display:inline"><input type="hidden" value="✓" name="utf8"></div>
    <label for="q">Search for:</label>
    <input type="text" name="q" id="q">
    <input type="submit" value="Search" name="commit">
</form>

哪个大神解释下？