Question

我有一个可以很好地创建的表列表。我希望能够通过单击父项上的编辑（转到edit.html.erb）然后单击“新建孩子”来创建子表。父表和子表之间的关系是has_and_belongs_to_many。

<%= button_to 'New Child', new_parent_child_path([@parent, @parent.children.build]), :method => :get %>

这是新子表单的链接，产生以下错误：

'undefined method `children' for nil:NilClass'

服务器日志给出了以下内容：

Started GET "/parents/1//children/new" for blah at blah
Processing by ChildrenController#new as HTML
  Parameters: {"parent_id"=>"1"}
  Rendered children/_form.html.erb (1.3ms)
  Rendered children/new.html.erb within layouts/application (1.9ms)
Completed 500 Internal Server Error in 4ms

ActionView::Template::Error (undefined method `children' for nil:NilClass):
    1: <%= form_for ([@parent, @parent.children.build]) do |f| %>
    2: 
    3: <div class = "field">
    4:   <%= f.label :Child_name %><br/>
  app/views/children      /_form.html.erb:1:in`_app_views_children__form_html_erb__2140243687_70034946643120'
  app/views/children/new.html.erb:3:in `_app_views_children_new_html_erb__655166082_70034947829100'

在子项new.html.erb中呈现的_form.html.erb如下：

<%= form_for ([@parent, @parent.children.build]) do |f| %>

<div class = "field">
  <%= f.label :Child_name %><br/>
  <%= f.text_field :ChildName %>
</div>

<div class = "field">
  <%= f.label :Child_email_address %><br/>
  <%= f.text_field :ChildEmail %>
</div>

<div class = "actions">
  <%= f.submit %>
</div>
<% end %>

（注意：这些表实际上并不称为父和子，我只是为了保密而使用这些名称。另外，请不要建议我使用has_many，我不感兴趣。）

编辑＃1：来自'ChildrenController'的代码

  def new
    @child = Child.new
  end

  def create
    @parent = Parent.find(params [:parent_id])
    @scout = @parent.children.build(params[:child])
    redirect_to parent_path(@parent)
  end

Answer 1

您需要在新操作中加入@parent = Parent.find(params[:parent_id])，因为您在new.html.erb模板中使用它。否则它将为零，@parent.children.build将无效。

Ruby on Rails - 以habtm关系创建子表

1 个答案: