Re: Data types like Money or Price
On Nov 6, 5:40 pm, Puppet_Sock <puppet_s...@hotmail.com> wrote:
On Nov 6, 9:16 am, bb <muralibal...@gmail.com> wrote:
[snip]
I have started hand coding all the required operators,
bounds checking etc. specific to my project requirement. (
inheritance heirarchy : MyDouble <- MyPrice <- MyMoney )
If you've got a careful and complete specification of how
your money class is supposed to behave, you are already
much farther along than the typical application involving
money. Eventually most such projects wind up here asking
how they get the roundoff of pennies correct. It's a lot
of fun telling them that I can't quite read their spec
from where I'm sitting, then having them say they don't
have a spec. Usually they get confused at that point.
At least in the EU, the spec is a given; EU directives say
exactly how you have to round the cents.
Just a suggestion: Consider whether you really need that
inheritance. Consider whether what you really want is a
Currency class. (Or maybe call it Cash or Money or some
such.) Then when you have a price you can make that class
contain a Currency as a data member.
His inheritance doesn't make any sense at all. Generally
speaking, you probably need: a general Decimal class, to handle
the basic arithmetic; a monitary value class (MoneyAmount, or
some such) which has a Decimal in its implementation (but
controls rounding, etc., in a specific way), and a third class
which has both a MoneyAmount and a currency indicator (Euro,
GBP, USD, etc.).
[...]
Without getting too much into your specific app it's hard to
know whether the inheritance is the correct approach.
These are values, so inheritance is almost certainly the wrong
approach.
--
James Kanze (GABI Software) email:james.kanze@gmail.com
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