rails：如何在rails中创建动态下拉框？ [英] rails:how to create dynamic drop-down box in rails?

问题描述

  class FeedbacksController< ApplicationController 
 def new 
 @feedback = Feedback.new 
 @subject = Subject.find_all_by_teacher_id（current_user.id）
 end 
 
 end 
  

这里是视图，



<％= form_for @feedback）do | f | ％>
<％= render'shared / error_messages'，object：f.object％>

<％= f.label：subject_id％>

<％= f.collection_select（：subject_id，@subject，：id，：name）％>

  f.label：strength％> 
<％= f.text_field：highlights％> 
 
<％= f.label：rating％> 
<％= f.radio_button：rating，'A'，：checked =>真实％> A 
<％= f.radio_button：rating，'B'％> B 
<％= f.radio_button：rating，'C'％> C 
<％= f.radio_button：rating，'D'％> D 
 
 
 
<％= f.label：recommendations％> 
<％= f.text_field：recommendations％> 
 
 
 
 
 
 
<％= f.submit创建我的帐户，class：btn btn-large btn- primary％> 
<％end％> 
  

我想创建第二个下拉框主题，系统将从DB.That的意思，当我选择另一个主题，这个下拉框也将更改

解决方案

例如，我有一个国家/地区表，其中包含
个国家/地区的名称，我正在为用户创建一个表单。在我需要所有
国家名称的形式应来自数据库动态，我将
使用所有名称选项在选择

当我在表单中创建新用户时，我将使用：

 ％label COUNTRY 
 = f.select：user_country，options_for_select（Country.order（：country_name）.pluck（：country_name））
 当我在表单中使用表单编辑现有用户时，我将使用  
 p> 
 
 
 ％label COUNTRY 
 = f.select：user_country，options_for_select（Country.order（：country_name）.pluck ），：selected => @ user.user_country）
  
 
class FeedbacksController < ApplicationController
    def new
    @feedback = Feedback.new
    @subject = Subject.find_all_by_teacher_id(current_user.id)
end

end
Here is view,

    
      
        <%= form_for(@feedback) do |f| %>
         <%= render 'shared/error_messages', object: f.object %>

      <%= f.label :subject_id %>

      <%= f.collection_select(:subject_id, @subject, :id, :name ) %>
  <%= f.label :strengths %>
  <%= f.text_field :strengths %>

  <%= f.label :rating %>
  <%= f.radio_button :rating, 'A', :checked => true %> A
  <%= f.radio_button :rating, 'B' %> B
  <%= f.radio_button :rating, 'C' %> C
  <%= f.radio_button :rating, 'D' %> D



  <%= f.label :recommendations %>
  <%= f.text_field :recommendations %>






  <%= f.submit "Create my account", class: "btn btn-large btn-primary" %>
<% end %>


I wanna to create a second drop-down box if chose a subject ,system will search students who have this subject from DB.That meaning when I choose another subject this drop-down box will also change
解决方案

  
Say for example I have a Country table which contains names of
  countries, and I am creating a form for user. In the form I need all
  countries name should come dynamically from database, and I will
  use all names as Options in Select
When I am using in form for creating a new user, I will use:
%label COUNTRY
      =f.select :user_country, options_for_select(Country.order(:country_name).pluck(:country_name))
When I am using in form for editing an existing user, I will use:
%label COUNTRY
  =f.select :user_country, options_for_select(Country.order(:country_name).pluck(:country_name), :selected=>@user.user_country)


                        
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