AJAX 对象创建，但直到手动刷新才出现答案

【问题标题】：AJAX Object Creating, but Not Appearing Until Manual RefreshAJAX 对象创建，但直到手动刷新才出现
【发布时间】：2016-06-13 21:24:33
【问题描述】：

我正在使用各种lists 构建一个基本的应用程序，每个has_many items。我正在尝试在列表创建上实现 AJAX 并在lists#index 页面上显示。新列表创建正常，但在我手动刷新页面之前它们不会出现。这是错误，如服务器日志中所述：

 List Exists (0.1ms)  SELECT  1 AS one FROM "lists" WHERE ("lists"."id" IS NOT NULL) AND "lists"."slug" = ? LIMIT 1  [["slug", "new-list-again"]]
  SQL (0.3ms)  INSERT INTO "lists" ("name", "shared_with", "user_id", "slug") VALUES (?, ?, ?, ?)  [["name", "New List Again"], ["shared_with", ""], ["user_id", 2], ["slug", "new-list-again-dc08b63c-1d57-42ea-a725-a2c5c185e529"]]
   (0.7ms)  commit transaction
  Rendered lists/create.js.erb (7.9ms)
Completed 500 Internal Server Error in 22ms (ActiveRecord: 1.4ms)

NoMethodError - undefined method `valid?' for nil:NilClass:
  app/views/lists/create.js.erb:1:in `_app_views_lists_create_js_erb___822718317456566494_70187652289300'

这是我lists#index页面上的相关代码：

<h1>My Lists (<%= @lists.count %>)</h1>
<% if @lists.count == 0 %>
  <p>You don't have any lists yet! Why don't we remedy that?<p>
<% end %>

<div class='list-form'>
  <%= render partial: 'lists/form', locals: { list: @list } %>
</div>

<div class="js-lists">
  <%= render @lists %>
</div>

这是我的lists/_form 部分：

<div class="row">
  <div class="col-xs-12">
    <%= form_for @list, format: :js, remote: true do |f| %>
      <div class="form-group col-sm-6">
        <%= f.label :name %>
        <%= f.text_field :name, class: 'form-control', placeholder: "Enter List Name" %>
      </div>

      <div class="form-group col-sm-6">
        <%= f.label 'Share My List (Not Required)' %>
        <%= f.text_field :shared_with, class: 'form-control', placeholder: "Enter Emails Separated by Commas" %>
      </div>

      <div class="text-center"><%= f.submit "Let's Go!", class: 'btn btn-primary' %></div>
    <% end %>
  </div>
</div>

这是我的lists/_list 部分：

<%= link_to list_path(list) do %>
  <h4><%= list.name %>
    <% if list.shared_with != "" %>
     (Shared)
    <% end %>
  <% end %>
 <small>( <%= list.items.count %> Items, <%= link_to "Edit", edit_list_path(list) %> | <%= link_to "Delete", list_path(list), method: :delete %> )</small></h4>

这是我的create.js.erb 文件：

<% if @item.valid? %>
  $('.js-lists').prepend("<%= escape_javascript(render partial: 'lists/list', locals: { list: @list }) %>");
  $('.list-form').html("<%= escape_javascript(render partial: 'lists/form', locals: { list: @new_list }) %>");
<% else %>
  $('.flash').prepend("<div class='alert alert-danger'><button type='button' class='close' data-dismiss='alert'>&times;</button><%= flash.now[:alert] %></div>");
  $('.new-list').html("<%= escape_javascript(render partial: 'lists/form', locals: { list: @list }) %>");
<% end %>

这是我的lists_controller 中的create 方法：

def create
    @list = List.new(list_params)
    @list.user = current_user
    @new_list = List.new

    if @list.save
      flash[:notice] = "Your list was saved successfully."
    else
      flash.now[:alert] = "Error creating list. Please try again."
    end

    respond_to do |format|
      format.js
    end
  end

我对 Ruby 比较陌生，但对 Javascript 非常陌生，所以如果有人能帮助指出我在哪里出错，我将不胜感激。新的list 肯定正在创建中，只是在您手动刷新页面之前它不会显示。

【问题讨论】：

标签： javascript ruby-on-rails ajax

【解决方案1】：

您在create.js.erb 中的变量名似乎有误。您应该检查@list 的有效性，而不是@item

【讨论】：

天哪，我知道这很愚蠢。谢谢。