轨道上的多级选择

我想在几个模型之间使用多个选择下拉列表

我有这个:

class Report < ActiveRecord::Base belongs_to :region end class City < ActiveRecord::Base has_many :regions end class Region < ActiveRecord::Base has_many :reports belongs_to :city end 

当我选择一个城市时,我想从所选城市中提取项目列表并在下一个下拉列表中显示。 如何在下拉菜单之间创建关系? 谁能帮我?

谢谢。

此链接可以帮助您完成此操作。

Rails 2 + Prototype

应用程序/模型/ cities.rb

 class City < ActiveRecord::Base has_many :regions has_many :reports, :through => :regions # this is newly added end 

cities_controller

 class CitiesController < ApplicationController def index @cities = City.find(:all) @regions = Region.find(:all) @reports = Report.find(:all) end def update_regions # updates regions and reports based on city selected city = City.find(params[:city_id]) regions = city.regions reports = city.reports render :update do |page| page.replace_html 'regions', :partial => 'regions', :object => regions page.replace_html 'reports', :partial => 'reports', :object => reports end end def update_reports # updates reports based on region selected region = Region.find(params[:region_id]) reports = region.reports render :update do |page| page.replace_html 'reports', :partial => 'reports', :object => reports end end end 

_reports.html.erb

 <%= collection_select(nil, :report_id, reports, :id, :title, {:prompt => "Select a Report"}) %> 

_regions.html.erb

 <%= collection_select(nil, :region_id, regions, :id, :name, {:prompt => "Select a Region"}, {:onchange => "#{remote_function(:url => {:action => "update_reports"}, :with => "'region_id='+value")}"}) %> 

index.html.erb

 <%= javascript_include_tag :defaults %> <%= collection_select(nil, :city_id, @cities, :id, :name, {:prompt => "Select a City"}, {:onchange => "#{remote_function(:url => {:action => "update_regions"}, :with => "'city_id='+value")}"}) %> 
<%= render :partial => 'regions', :object => @regions %>
<%= render :partial => 'reports', :object => @reports %>