From: 13 <one.three@...>
Date: 2006-04-29T00:16:48+09:00
Subject: Re: class returns value without method or attribute

Hi,

Here is my approach (similar, but longer):

$ cat money.rb

class Money
  attr_accessor :value

  def initialize(value)
    @value = value
  end

  def to_s
    @value.to_s
  end

  def +(other)
    case other
      when Money:
        Money.new(@value + other.value)
      when Numeric:
        Money.new(@value + other)
      else
        raise "Money can be added to Money or Numeric"
    end
  end
end

irb(main):002:0> money = Money.new 5
=> #<Money:0x2ba41c8 @value=5>
irb(main):004:0> puts money
5
irb(main):005:0> puts money + money
10
irb(main):006:0> puts money + 100
105
irb(main):007:0> puts money + 'money'
RuntimeError: Money can be added to Money or Numeric
        from ./money.rb:19:in `+'
        from (irb):7

--
Martins

On 4/28/06, Farrel Lifson <farrel.lifson@gmail.com> wrote:
> You could overload the  methods you require.  For instance if you want
> to be able to add two Money objects togeter and get a Money object as
> the result using the expression 'money1 + money2' you could do
>
> >> class Money
> >>   attr_accessor :value
> >>   def+(other)
> >>     Money.new(@value + other.value)
> >>   end
> >>   def initialize(value)
> >>     @value = value
> >>   end
> >> end
> => nil
> >> m1 = Money.new(5)
> => #<Money:0x2dbb018 @value=5>
> >> m2 = Money.new(10)
> => #<Money:0x2db9098 @value=10>
> >> m1 + m2
> => #<Money:0x2db17d8 @value=15>
>
> Farrel
>
>