ruby-on-rails - 默认情况下 simple_form - collection_check_boxes 在末尾显示 hidden_​​field

Question

我在 new.html.erb 中使用 simple_form 的 collection_check_boxes。默认情况下，当 html 被渲染时，它会在最后添加隐藏字段，因为在 Controller 端我得到最后一个元素为“”的值数组。任何人都可以帮助我如何防止隐藏字段在 View 上呈现？

新的.html.erb:

<%= f.collection_check_boxes :topic_id, Topic.all, :id, :name %>
<%= f.button :submit %>

我使用 Firebug 检查我的复选框元素，结果如下:

    <span>
    <span>
    <input type="hidden" value="" name="revision[topic_id][]">
    <input class="btn" type="submit" value="Create Revision" name="commit">

我想删除上面的隐藏字段。请帮忙。

Answer 1

隐藏字段是故意存在的，您可能不想删除它。用于处理未选中复选框的情况。

我认为 simple_form 最终会回到标准 FormBuilder 中相同的基本 check_box 逻辑上。这里有一些文档说明了为什么复选框具有该隐藏字段。从 check_box documentation :

# The HTML specification says unchecked check boxes are not successful, and
# thus web browsers do not send them. Unfortunately this introduces a gotcha:
# if an +Invoice+ model has a +paid+ flag, and in the form that edits a paid
# invoice the user unchecks its check box, no +paid+ parameter is sent. So,
# any mass-assignment idiom like
#
#   @invoice.update(params[:invoice])
#
# wouldn't update the flag.
#     
# To prevent this the helper generates an auxiliary hidden field before
# the very check box. The hidden field has the same name and its
# attributes mimic an unchecked check box.
#
# This way, the client either sends only the hidden field (representing
# the check box is unchecked), or both fields. Since the HTML specification
# says key/value pairs have to be sent in the same order they appear in the
# form, and parameters extraction gets the last occurrence of any repeated
# key in the query string, that works for ordinary forms.

标准 collection_check_boxes 的 example 显示隐藏字段:

# Sample usage (selecting the associated Author for an instance of Post, <tt>@post</tt>):
#   collection_check_boxes(:post, :author_ids, Author.all, :id, :name_with_initial)
#
# If <tt>@post.author_ids</tt> is already <tt>[1]</tt>, this would return:
#   <input id="post_author_ids_1" name="post[author_ids][]" type="checkbox" value="1" checked="checked" />
#   <label for="post_author_ids_1">D. Heinemeier Hansson</label>
#   <input id="post_author_ids_2" name="post[author_ids][]" type="checkbox" value="2" />
#   <label for="post_author_ids_2">D. Thomas</label>
#   <input id="post_author_ids_3" name="post[author_ids][]" type="checkbox" value="3" />
#   <label for="post_author_ids_3">M. Clark</label>
#   <input name="post[author_ids][]" type="hidden" value="" />