Feedback on current ORM-implementation.

[sweatje]

Is this wrong?

Not wrong, but it makes money an entity rather than a value object.

[nacho]

Yes, it does. I guess I could live with it though.

[johno]

The only thing I have against the whole "doing it from SQL" is the fact that it's Objects we're mapping onto SQL and not the other way around. I'm realy considering an XML-approach just to get all the features I wan't without tying me to a specific DB.

I would definitely go the way defining schema in PHP (lastcrafts aproach) or XML. You can add this MySQL5 specific stuff anytime.

[lastcraft]

Hi...

Yes, it does. I guess I could live with it though.

In the context of persistence it will drive you mad.

Regarding Money being made up of the amount and the currency, Postgres has a composite type facility. I think other database systems (not MySQL) have similar facilities.

Going the XML route will solve this problem quite easily. I managed to get "Changes" to return objects of arbitrary classes, and it's espcially easy if you are using serialisation.

yours, Marcus

[Selkirk]

Off Topic:

Associating quantity and units is a more general domain pattern. For example, in continuous process manufacturing, one cannot express quantity without units. You can order 7 tractors, but you cannot order 7 molasses. In some industries the potential for rounding errors means that you always have to associate quantity and units. In my old industry, one could never leave behind the units expressed on the order, say by converting to a common unit. The resulting rounding errors could (and historically had) result in product that exceeded the capacity of its container.