1、变量和常量：
全局变量用$; 实例变量用@; 类变量用@@;
Local Variable: name fish_and_chips x_axis thx1138 _x _26
Instance Variable: @name @point_1 @X @_ @plan9
Class Variable: @@total @@symtab @@N @@x_pos @@SINGLE
Global Variable: $debug $CUSTOMER $_ $plan9 $Global
Class Name: String ActiveRecord MyClass
Constant Name: FEET_PER_MILE DEBUG
2、数组
a = [ 'ant', 'bee', 'cat', 'dog', 'elk' ]
a[0] # => "ant"
a[3] # => "dog"
# this is the same:
a = %w{ ant bee cat dog elk }
a[0] # => "ant"
a[3] # => "dog"
