a preamble to Building a Cascading Drop Down Selection List for Ruby on Rails with jQuery Ajax

This is a preamble to the last years post Building a Cascading Drop Down Selection List for Ruby on Rails with jQuery Ajax, In part because I’ve realized that people where are lost without some basic setup I assumed as given. So here I’m giving it, explicitly.

Directions here are valid for Ruby 1.8, Ruby on Rails 2.3.5 and jQuery 1.4.2, and I still going for “The Simplest Thing That Will Work” (TSTTWW)

First generate scaffolding for Section (with name as columns) and Sub_Section (with name and section_id as columns)


>script/generate scaffold Sections name:string

>script/generate scaffold Sub_Sections name:string section_id:integer

Then run Migration to create these 2 tables in your database

>rake db:migrate

Modify the models to account for the association between the model and very basic validation

class Section < ActiveRecord::Base has_many :sub_section validates_presence_of :name end class SubSection < ActiveRecord::Base belongs_to :section validates_presence_of :name, :section_id end
Modify the Sub_section New view to allow the selection of a Section name and the population of the model with a valid Section Id, but blank by default

the edit view needs to modified as well to show the selected value but allow you to change it

Modify the Sub_section index view to show the Section Name’s

and Modify the Show view as well it include the section name

So now things are setup to populate the Sections and SubSection by adding (for example Sections : Meat,

Vegetables, Fruit) and Subsections {Beef, Meat} and {Apple , Fruit}, {Pork, Meat}, etc…..

Which can be used elsewhere like a Gallery model, viewer and controler


>script/generate scaffold Gallery name:string section_id:integer sub_section_id:integer


run Migration to create this table in your database

>rake db:migrate

change the Gallery model to add the association for Section_id and sub_section_id field and add the validation

belongs_to :section
belongs_to :sub_section
validates_presence_of :name, :section_id, :sub_section_id


Add Jquery to the public/javascript library and Modify the layout of Gallery to include it in your views foe test with

< %= javascript_include_tag 'jquery-1.4.2.min.js' %>


from there the directions on the orginal post Building a Cascading Drop Down Selection List for Ruby on Rails with jQuery Ajax apply.

Update : a April 2015 article is a worthy update : Dynamic Duos – Dependent Select Menus with JQuery and Rails (and links back to the orginal post!)