Dynamic Select with ancestry

问题

My application using ancestry gem.

class Location < ActiveRecord::Base
 has_ancestry :cache_depth => true
 has_many :posts
end

class User < ActiveRecord::Base
 belongs_to :location
end

I created some random Location,

Alaska
California
- Los Angeles
- Fresno
  - Cincotta (Fresno)
  - Hammond (Fresno)
  - Melvin (Fresno)

My question if user sign up form if User select California, display child Los Angles and Fresno, after select Fresno then display it's child.

I got javascript tutorial for Dropdown list http://www.plus2net.com/javascript_tutorial/dropdown-list-demo.php

How is possible work with ancestry gem?

回答1:

Nested

Firstly, if you wanted to keep them all in a single dropdown, we created the following helper which achieves it for you:

#app/helpers/application_helper.rb
def nested_dropdown(items)
    result = []
    items.map do |item, sub_items|
        result << [('- ' * item.depth) + item.name, item.id]
        result += nested_dropdown(sub_items) unless sub_items.blank?
    end
    result
end

This will allow you to call:

<%= f.select(:category_ids, nested_dropdown(Category.all.arrange), prompt: "Category", selected: @category ) %>

This will give you the ability to call a single dropdown, which has been nested according to your ancestry associations

Ajax

If you want to have double dropdown boxes, you'll probably have to implement an ajax function to pull the required data each time the initial dropdown changes:

#config/routes.rb
resources :categories do
    get :select_item
end

#app/assets/javascripts/application.js
$("#first_dropdown").on("change", function(){
   $.ajax({
       url: "categories/"+ $(this).val() + "/select_item",
       dataType: "json",
       success: function(data) {
          //populate second dropdown
       }
   })
});

#app/controllers/categories_controller.rb
Class CategoriesController < ApplicationController
    respond_to :json, only: :select_item

    def select_item
       category = @category.find params[:category_id]
       respond_with category.children
    end
end