Ruby on Rails:获得一个空的额外记录?

I noticed that when I create a record in one of my tables, and I have some kind of data that is associated with that table, it adds 1 record already, but it is nil?

我注意到，当我在一个表中创建一条记录时，我有一些与该表相关的数据，它已经添加了一条记录，但它是nil?

For instance:

例如:

lists controller

列出了控制器

  def show
    @list = List.find(params[:id])
    @idea = @list.ideas.build
    respond_to do |format|
      format.html # show.html.erb
      format.json { render json: @list }
    end
  end

list model

列表模式

has_many :ideas

idea model

概念模型

belongs_to :list

list > show.html.erb

列表> show.html.erb

<%= @list.ideas.each do |idea| %>
  <div>
    <div class="list_idea_desc"><%= idea.description %></div>
    <div><%= link_to 'Show', idea %></div>
    <div><%= link_to 'Destroy', idea, method: :delete, data: { confirm: 'Are you sure?' } %>   </div>
  </div>
<% end %>

I get this record:

我得到这个记录:

[#<Idea id: nil, name: nil, description: nil, 
picture: nil, created_at: nil, updated_at: nil, list_id: 1>]

This idea record automatically gets inserted into my database when I create a new list. Why does this happen?

当我创建一个新列表时，这个想法记录会自动插入到我的数据库中。这为什么会发生?

3 个解决方案

#1

Difference between new and build is that build adds the newly created object to the collection:

new和build之间的区别在于build将新创建的对象添加到集合中:

Replace:

替换:

@idea = @list.ideas.build

With:

:

@idea = @list.ideas.new

---

Or if you want to use build only, you should

或者如果您想只使用build，您应该这样做

Replace:

替换:

<%= @list.ideas.each do |idea| %>

With:

:

<%= @list.ideas(true).each do |idea| %>

true discards the cached copy of ideas and goes back to the database.

true会丢弃想法的缓存副本并返回数据库。

#2

This is due to @idea = @list.ideas.build code line, remove it and check it. It may works for your view.

这是由于@idea = @list.ideas。构建代码行，删除它并检查它。它可能适合你的观点。

<% @idea = @list.ideas.build %>
<%= form_for [@list,@idea] do |f| %>

#3

Try this:

试试这个:

<%= @list.ideas.each do |idea| %>
  <% if idea.present? %>
  <div>
    <div class="list_idea_desc"><%= idea.description %></div>
    <div><%= link_to 'Show', idea %></div>
    <div><%= link_to 'Destroy', idea, method: :delete, data: { confirm: 'Are you sure?' } %>                   </div>
  </div>
  <% end %>
<% end %>

Use present? condition in record saving time also.

用礼物吗?记录保存时间的条件。