Rails - 在表单中显示外键引用 [英] Rails - Displaying Foreign Key References in a form

问题描述

我正在用两种模式做一个简单的练习。体育和团队，定义为

 
 rails g scaffold体育名称：整数
 rails g scaffold球队名称：整数球迷：整数运动：引用
 

（注意：我使用脚手架的原因是快速原型设计，所以我可以学习/实验我不是熟悉了）

问题是我的运动（即外键引用）显示如下

所以它很奇怪＃< ; blahl blah> notation to it ...

 <％= form_for（@team） do | f | ％GT; 
 <％if @ team.errors.any？ ％GT; 
< div id =error_explanation> 
< h2><％= pluralize（@ team.errors.count，error）％>禁止保存此团队：< / h2> 
 
< ul> 
<％@ team.errors.full_messages.each do | msg | ％GT; 
< li><％= msg％>< / li> 
<％end％> 
< / ul> 
< / div> 
<％end％> 
 
< div class =field> 
<％= f.label：name％>< br /> 
<％= f.text_field：name％> 
< / div> 
< div class =field> 
<％= f.label：fans％>< br /> 
 <％= f.number_field：fans％> 
< / div> 
< div class =field> 
<％= f.label：sport％>< br /> 
<％= f.text_field：sport％> 
< / div> 
< div class =actions> 
<％= f.submit％> 
< / div> 
<％end％> 
  

我尝试将一行更改为 @ team.sport.name 但它会导致错误未定义方法'Ice Hockey'for＃< Team：0x3e7e040> ...任何想法如何正确显示名称从这里开始

解决方案

您正在使用 text_field 来引用现有的对象，一个选择与运动作为选项在这里更合适。

这是它必须是改变：

 < div class =field> 
<％= f.label：sport％>< br /> 
<％= f.text_field：sport％> 
< / div> 
  

收件人：

 < div class =field> 
<％= f.label：sport％>< br /> 
<％= f.select：sport_id，options_for_select（Sport.all.map {| s | [s.name，s.id]}）％> 
< / div> 
  

f.select 会生成一个select在HTML中，这些选项将使我在数据库中的所有运动。

• http://apidock.com/rails/ActionView/ Helpers / FormOptionsHelper / select


• http://guides.rubyonrails.org/form_helpers.html#select-boxes-for-dealing-with-models

更简洁的方法是在控制器中设置一个变量 @sports ，然后在视图中调用它：

 ＃在控制器中$＃$ b def编辑
 @sports = Sport.scoped 
＃... 
 
＃编辑视图
< div class =field> 
<％= f.label：sport％>< br /> 
 <％= f.select：sport_id，options_for_select（@ sports.map {| s | [s.name，s.id]}）％> 
< / div> 
  

---

附加信息：如果你想为选择预先选择一个选项，你必须将它作为 options_for_select helper的第二个参数传递：

  options_for_select（@ sports.map {| s | [s.name，s.id]}，params [：sport_id]）
＃默认选择与params [：sport_id]相同的选项
  

I'm doing a simple exercise with two models. Sport and Teams, defined as

rails g scaffold sport name:integer
rails g scaffold team name:integer fans:integer sport:references

(Note: The reason I'm using scaffold is rapidly prototyping so I can learn/experiment with the parts I'm not familiar with yet)

Problem is that my "sport" (i.e. the foreign key reference) is showing like the following

So it's got that weird #<blahl blah> notation to it...

<%= form_for(@team) do |f| %>
  <% if @team.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@team.errors.count, "error") %> prohibited this team from being saved:</h2>

      <ul>
      <% @team.errors.full_messages.each do |msg| %>
        <li><%= msg %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="field">
    <%= f.label :name %><br />
    <%= f.text_field :name %>
  </div>
     <div class="field">
    <%= f.label :fans %><br />
    <%= f.number_field :fans %>
  </div>
  <div class="field">
    <%= f.label :sport %><br />
    <%= f.text_field :sport %>
  </div>
  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

I've tried changing the one line to @team.sport.name but it results in an error undefined method 'Ice Hockey' for #<Team:0x3e7e040>... Any ideas how to properly display name from here??

解决方案

You are using a text_field for referencing an existing object, a select with Sports as options would be more appropriate here.

This is where it has to be changed:

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

To:

<div class="field">
  <%= f.label :sport %><br />
  <%= f.select :sport_id, options_for_select(Sport.all.map{|s|[s.name, s.id]}) %>
</div>

The f.select will generate a select box in HTML, the options will me all the sports in your DB.

Some documentation about it:

• http://apidock.com/rails/ActionView/Helpers/FormOptionsHelper/select
• http://guides.rubyonrails.org/form_helpers.html#select-boxes-for-dealing-with-models

A cleaner way would be to set a variable @sports in your controller and call it then in your views:

# in controller
def edit
  @sports = Sport.scoped
  #...

# in edit view
<div class="field">
  <%= f.label :sport %><br />
  <%= f.select :sport_id, options_for_select(@sports.map{ |s| [s.name, s.id] }) %>
</div>

---

Additionnal information: If you want to "pre-select" an option for the select, you have to pass it as the second argument of the options_for_select helper:

options_for_select(@sports.map{ |s| [s.name, s.id] }, params[:sport_id])
# this will select by default the option that matches the value of params[:sport_id]

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