From: Robert Klemme <shortcutter@...>
Date: 2008-02-10T02:30:00+09:00
Subject: Re: Inheriting from / Delegating to Integer - Currency class   implementation

On 09.02.2008 15:25, Pascal Ehlert wrote:
> On 2/9/2008 Rick DeNatale wrote:
>>   def coerce(other)
>>     [self, other.to_currency]
>>   end
> 
> Whoa, that looks really interesting.
> Thanks a lot, Rick!
> 
> However, is there another way to implement the Currency class using 
> DelegateClass?

There might be but you will have to handle type differences anyway.  You 
will have to implement #coerce, #+ etc. in any case.  I recommend to use 
Rick's approach because it is much cleaner.

> It still feels wrong to me to write +, -, * and / on my own, although 
> they are exactly the same as in the Integer class.

Actually, they are not the same.  Adding currencies is significantly 
more complex than adding ints.  What happens if you add 5 EUR and 12 
USD?  All sorts of issues are lurking here.  A currency value is (at 
least) a decimal value and a currency identifier - at least this is the 
most straightforward definition I can think of.  You are doing yourself 
a favor by doing it properly - it's not that difficult.

Kind regards

	robert