Re: Business objects, subset of collection

By the way, what is your RAD IDE of choice?

For the last 20 years before retiring I was an R-T/E guy so the only RAD
problems we saw were support tools for the software process (e.g.,
defect tracking). For that mundane stuff I usually used Access. I
haven't looked at the market so I wouldn't know what to use for
something like a web-based POS where one has both networking and server
issues. (There wasn't much around back in the '70s when I was doing IT,
but I'm sure we've come a long way since.)

When you say "When I need to solve a CRUD/USER problem I forget about
OO and use a RAD IDE", you are talking about MS Access? Since you
frequently refer to RAD IDE as the silver bullet for everything that
the OO model can't solve, it is a little big surprisingly that the
only RAD IDE you have experience from is MS Access. Don't you think
there are something between the OO approach and MS Access?

Currently there are very few RAD IDE's that actually provide some
value in software development. They simply not powerful enough.
Instead you have to use a normal programming language and use embedded
SQL for data management tasks. The 3GL host language should mainly
focus on presentation and communication. The more business logic you
can put into views, the cleaner your application will be. Unpaid
invoices as an example:

create view invoice_balance as
select i.invoiceid, i.amount - sum(p.amount)
from payment p
join invoice i on i.invoiceid=p.invoiceid
group by i.invoiceid

Using such view, you call "select balance from invoice_balance where
invoiceid=?", whereever in your application, reusing the business
logic above.

//frebe
.