app\models\setting.rb :165
  # fixed domain url in development. tantantan's bug
  if Rails.env.development?
    methods.map do |m|
      define_singleton_method m do; nil; end if m.to_s =~ /([a-zA-Z]+_domain)$/
    end
  end
  程序部分链接中制定了subdomain参数，使链接在二级域名中来回跳转。
  为了开发方便，使之功能在development模式下失效。 
  # => nyan
================================================================================
#导航栏匹配域名显示和改变
app\helper\application_helper.rb
# rewrite navigation 

app\views\layouts\_base_header.html.erb
# reset navigation by domain name and url through regular match
================================================================================
#首页根据域名匹配进入不同的页面
app\controller\welcome_controller.rb
  def entry_select_user
    if request.original_url.match(/user\.trustie\.net/)
      redirect_to(:controller => "users", :action => "index")
      return 0
    end
  end
================================================================================