小编Fre*_*red的帖子

我有以下Ruby程序:

require 'date'

class Person

 def initialize(name, dob)
  @name = name
  @dob = dob
 end

 def age
  Time.now - @dob
 end

 def marry(someone)
  "Life: " + age.to_s
 end

end

fred = Person.new('Fred', Date.new(1934, 4, 16))
p fred
p fred.age.to_s
p fred.marry(1)

但是ruby 1.9.2给出了错误:

#<Person:0x2afab78 @name="Fred", @dob=#<Date: 1934-04-16 (4855087/2,0,2299161)>>
test1.rb:11:in `-': can't convert Date into an exact number (TypeError)
        from test1.rb:11:in `age'
        from test1.rb:22:in `<main>'

我究竟做错了什么？TIA