Ruby on Rails - drop down box on change event

Question

I have two drop down boxes in my application. Based on the value selected in 1st combobox, the values in 2nd drop down box should be populated.And these values should come f

Answer 1

here's a clean approach using jquery-ujs (https://github.com/rails/jquery-ujs)

In your view:

<%= 
  select_tag  
      :first_select, # name of selectbox
      options_from_collection_for_select(@myrecords, "id", "name"), # your options for this select box
      :'data-remote' => 'true', # important for UJS
      :'data-url' => url_for(:controller => 'MyController', :action => 'getdata'), # we get the data from here!
      :'data-type' => 'json' # tell jQuery to parse the response as JSON!
%>


<%= 
   select_tag  
       :second_select, # name of selectbox
       "<option>Please select something from first select!</option>"
%> 

Your Controller:

class MyController < ApplicationController


  def getdata
    # this contains what has been selected in the first select box
    @data_from_select1 = params[:first_select]

    # we get the data for selectbox 2
    @data_for_select2 = MyModel.where(:some_id => @data_from_select1).all

    # render an array in JSON containing arrays like:
    # [[:id1, :name1], [:id2, :name2]]
    render :json => @data_for_select2.map{|c| [c.id, c.name]}
  end
end

In your application.js:

$(document).ready(function() {

  // #first_select is the id of our first select box, if the ajax request has been successful,
  // an ajax:success event is triggered.

  $('#first_select').live('ajax:success', function(evt, data, status, xhr) {
    // get second selectbox by its id
    var selectbox2 = $('#second_select');

    // empty it
    selectbox2.empty();

    // we got a JSON array in data, iterate through it

    $.each(data, function(index, value) {
      // append an option
      var opt = $('<option/>');

      // value is an array: [:id, :name]
      opt.attr('value', value[0]);
      // set text
      opt.text(value[1]);
      // append to select
      opt.appendTo(selectbox2);
    });
  });

});

Answer 2

This is how I did it. Works in Rails 3.2

View:

<%= select_tag :major_category_select_id, options_from_collection_for_select(@majorcategories, 'id', 'name'), :'data-remote' => 'true', :'data-url' => url_for(:controller => 'listings', :action => 'submit_major_category', format: 'js') %>

Controller method:

def submit_major_category
    @major_category = MajorCategory.find(params[:major_category_select_id])
    @minor_categories = @major_category.minor_categories

    respond_to do |format|
      # format.html { render partial: 'minor_categories_select' }
      format.js
    end
  end

Routes:

get "listings/submit_major_category"

Then create a submit_major_category.js.erb file that gets responded to.

Answer 3

You could take inspiration from what I have in a project of mine. It updates the state given the country selected. It makes use of Carmen a great gem listing countries, states etc...

View:

<p>
  <label>Country <span>*</span></label>
  <%= profile_form.select(:country,Carmen.countries, {:include_blank => 'Select a Country'}, :id => "profile_country") %>
</p>
<p>
  <label>State <span>*</span></label>
  <%= profile_form.select(:state,  "" , {:include_blank => 'Select a Country first'}, :id => "profile_state") %>
</p>

Jquery code:

$('#profile_country').change(function() {
  if ($(this).val() == '')
    {
    $('#profile_state').html( $('<option>No state provided for your country</option>'));
    }
  else {
   $.ajax({
    type: "GET",
    url: "/remote/get_states/" + encodeURIComponent($(this).attr('value')),
    success: function(data){
       if (data.content == 'None')  //handle the case where no state related to country selected
         {
         $('#profile_state').empty();
         $('#profile_state').append( $('<option>No state provided for your country</option>'));
         }
        else
         {
         $('#profile_state').empty();
         $('#profile_state').append( $('<option>Select your State</option>'));
         jQuery.each(data,function(i, v) {
           $('#profile_state').append( $('<option value="'+ data[i][1] +'">'+data[i][0] +'</option>'));
         });
       }
     }
   });
 }
});

Controller:

def states
  begin
    render :json => Carmen::states(CGI::unescape(params[:country]))
  rescue 
    render :json => {"content" => "None"}.to_json
  end
end