rails完美实现中国省市区三级联动

　　　完美实现中国省市区ajax三级联动．

　　　一，下载MYSQL的数据库表 ，分别有三个province city area,

　　　二，在helpers当中加入一个方法，取出全国省：

def get_area_select_options
      Province.find(:all,:order=>'province').collect{|item|[item.province,item.provinceid]}.insert(0,["请选择..",nil])     
    end

         三,在views当中，比如new的form当中需要加入如下语句：

<p><label for="friend_level2_provice_id">所在城市</label><br/>
  <%= select("friend_level2", "provice_id", get_area_select_options, {}, { "onchange" => remote_function(   
        :with => "'parent_id='+value",
        :update => 'next_select',
        :complete => "Element.hide('county_select')",
        :url => { :action => :select_with_ajax } ) })%>
  <span id='next_select'>         
  </span>  
  <span id='county_select'> </span> 
  <br/>
</p>

 　　四，分别在对应的controllers当中加入如下语句：

def select_with_ajax       
    @citys = [["请选择",""]]+City.find(:all, :conditions => ["fatherid = ?", params[:parent_id]]).collect { |item| [item.city, item.cityid] }           
    render(:layout => false)        
  end
  def select_with_ajax1       
    @areas = Area.find(:all, :conditions => ["fatherid = ?", params[:parent_id]]).collect { |item| [item.area, item.areaid] }      
    render(:layout => false)   
  end

 　　五，在views创建两个rhtml分别是：select_with_ajax，代码如下：

<%= select("friend_level2", "city_id", @citys, {}, { "onchange" => remote_function(   
        :with => "'parent_id='+value",
        :update => 'county_select',
        :complete => "Element.show('county_select')",
        :url => { :action => :select_with_ajax1 } ) })%>

 　　　另外一个是select_with_ajax1，代码如下：

<%= select("friend_level2", "area_id", @areas) %> 

 　　六，我目的表结构是:

 

CREATE TABLE `friend_level2s` (
  `id` int(10) unsigned NOT NULL auto_increment,  
  `provice_id` int(11) default NULL,
  `city_id` int(11) default NULL,
  `area_id` int(11) default NULL,
  PRIMARY KEY  (`id`)  
) ENGINE=MyISAM AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;

      另外，如果有乱码请在application.rb当中加入如下语句：

 before_filter :configure_charsets
  def configure_charsets
    @response.headers["Content-Type"] = "text/html; charset=utf-8"
    # Set connection charset. MySQL 4.0 doesn’t support this so it
    # will throw an error, MySQL 4.1 needs this
    suppress(ActiveRecord::StatementInvalid) do
      ActiveRecord::Base.connection.execute 'SET NAMES UTF8'
    end 
  end 

 　使用说明，完美实现了动态查询中国省市区的联动！呵呵，好好学习．