image_tag, path, url

http://api.rubyonrails.com/classes/ActionView/Helpers/AssetTagHelper.html


  ActionController::Base.asset_host = "assets.example.com"
  image_tag("rails.png")
    => <img src="http://assets.example.com/images/rails.png" alt="Rails" />
  stylesheet_link_tag("application")
    => <link href="http://assets.example.com/stylesheets/application.css" media="screen" rel="stylesheet" type="text/css" />


  ActionController::Base.asset_host = Proc.new { |source| "http://assets#{rand(2) + 1}.example.com" }
  image_tag("rails.png")
    => <img src="http://assets2.example.com/images/rails.png" alt="Rails" />
  stylesheet_link_tag("application")
    => <link href="http://assets1.example.com/stylesheets/application.css" media="screen" rel="stylesheet" type="text/css" />


  ActionController::Base.asset_host = Proc.new { |source|
     if source.starts_with?('/images')
       "http://images.example.com"
     else
       "http://assets.example.com"
     end
   }
  image_tag("rails.png")
    => <img src="http://images.example.com/images/rails.png" alt="Rails" />
  stylesheet_link_tag("application")
    => <link href="http://assets.example.com/stylesheets/application.css" media="screen" rel="stylesheet" type="text/css" />


  ActionController::Base.asset_host = Proc.new { |source, request|
    if request.ssl?
      "#{request.protocol}#{request.host_with_port}"
    else
      "#{request.protocol}assets.example.com"
    end
  }