Ruby類變量是空

我定義了一堆類變量在我的Ruby類，並將其初始化爲一個值，但是當我打印出來，我to_url功能他們都爲空，誰能告訴我，爲什麼???Ruby類變量是空

class BarChart < GoogleChart 
    @axes_prefix  = "chxt=" 
    @data_scale_prefix = "chds=" 
    @type    = "#@@type_prefix" + "bvg" 
    @size    = "#@@size_prefix" + "800x375" 
    @colors   = "#@@color_prefix" + "4466AA" 
    @axes    = "#@axes_prefix" + "x,y,x,y" 
    @x_axis_index  = "0" 
    @y_axis_index  = "1" 
    @x_axis_label_index = "2" 
    @y_axis_label_index = "3" 
    @axes_label_position_prefix = "chxp=" 
    @axis_range_prefix   = "chxr=" 

    def initialize(title, data, labels, x_axis_label, y_axis_label) 
     @title, @data, @labels, @x_axis_label, @y_axis_label = 
      title, data, labels, x_axis_label, y_axis_label 
     super(@title, @type, @size) 
     to_url() 
    end 


    def to_url() 
     puts @axes_prefix, @data_scale_prefix, @type, @size, @colors, 
     @axes, @x_axis_label_index, @y_axis_label_index, @x_axis_index, @y_axis_index 
    end 


    def start() 
    b = BarChart.new("CHART", "0,1,2,3,4,5,6,7,8,9", 
    "ZERO, ONE, TWO, THREE, FOUR, FIVE, SIX, SEVEN, EIGHT, NINE", 
    "Zero to Nine", "Numbers").to_s() 
    end 

if __FILE__ == $0 
    start() 
end

任何想法都會很棒。

謝謝。

來源

2011-07-25 Hunter McMillen