Question

我正在尝试创建一个允许创建Comment和相关附件的单个表单

评论模型有：

class Comment < ActiveRecord::Base
  has_many :attachments
  accepts_nested_attributes_for :attachments    
end

评论控制器：

  # GET /comments/new
  # GET /comments/new.json
  def new
    @comment = Comment.new
    @worequest = params[:worequest_id]

    respond_to do |format|
      format.html # new.html.erb
      format.json { render json: @comment }
    end
  end

在评论表格中，我试图添加：

<%= simple_form_for @comment, :html => {:class => 'form-horizontal'} do |f| %>
  (CODE FOR COMMENT)
  <% f.fields_for @attachments do |builder| %>
    <%= builder.input :name, :label => 'Attachment Name' %>
    <%= builder.file_field :attach, :label => 'Attachment File' %>
  <% end %>

但是，我收到了这个错误：

undefined method `model_name' for NilClass:Class

感谢您的帮助！

Answer 1

正如@Donovan评论的那样，你没有定义@attachments，因此错误。我猜这个错误来自form_for声明。

更新您的控制器new操作代码以在@comment上构建附件：

  # GET /comments/new
  # GET /comments/new.json
  def new
    @comment = Comment.new
    @comment.attachments.build # Add this line

    @worequest = params[:worequest_id]

    respond_to do |format|
      format.html # new.html.erb
      format.json { render json: @comment }
    end
  end

然后将表单视图代码更新为：

<%= simple_form_for @comment, :html => {:class => 'form-horizontal'} do |f| %>
  (CODE FOR COMMENT)
  <%= f.fields_for :attachments do |builder| %>
    <%= builder.input :name, :label => 'Attachment Name' %>
    <%= builder.file_field :attach, :label => 'Attachment File' %>
  <% end %>

您还可以选择在控制器操作中定义@attachments，然后在视图中使用它。通过执行当前对象的f.fields_for :attachments（在这种情况下为@comment），使用附件关联，因此不需要在控制器中定义@attachments。

Rails accepts_nested_attributes给出了未定义的方法

1 个答案: