# stuttle@xxxxxxxxx / 2006-10-11 21:28:36 +0100:
> Richard Lynch wrote:
> >On Tue, October 10, 2006 6:14 pm, Chris de Vidal wrote:
> >>I want to create a "customer" class which fetches its attributes from
> >>a MySQL database.
> >
> >No, you don't. :-)
> >
> >This is a classic example of the "obvious" OOP solution being wildly
> >inappropriate.
>
> Ok, so I now find myself in the unusual position of disagreeing with the
> Lynchmeister. Why is this wildly inappropriate? IMHO this is what OOP is
> all about.
No, that's what trivial OOP examples applied to the letter where
a different approach is in order are. If you study the GoF book [GoF]
you'll see that the traditional claim "objects model physical
entities from real world (and nothing else)" is very simplistic
and terribly limiting.
[GoF] http://www.amazon.com/dp/0201633612/
If you paint yourself into this corner you'll find your code
grinding the database to death in the OO-relational impedance
mismatch. The OOP ideal of a single source of data is nice,
unfortunately the real world gets in the way.
> You can encapsulate everything to do with a customer in an object. This
> ensures that you don't duplicate any code that works on customer data.
> You avoid duplication of code. As a result you can ensure data integrity
> because there is only one route to read and write it.
Who talks about duplicating business logic? You just need to have
more than one access point for the data.
> If this is not what you think OOP is all about, do please enlighten us
> as to the error of our ways.
Imagine deleting many rows in a table one by one (pseudocode):
class Record
{
function __construct($id)
{
$this->id = $id;
}
function delete()
{
// DELETE FROM some_table WHERE id = $this->id
}
}
foreach ($records as $r) {
$r->delete();
}
instead of taking them with a single DELETE:
// assuming
// class Search;
// $searchBuilder = new SearchBuilder;
// $SearchBuilder->add(new LessThan('id', '5000001'));
// $search = $searchBuilder->result();
class RecordSet
{
function __construct(Search $search)
{
$this->search = $search;
}
function delete()
{
// DELETE FROM some_table WHERE $this->search->toSQL()
}
}
$recordset($search);
$recordset->delete();
--
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You don't know, man. You don't KNOW.
Cause you weren't THERE. http://bash.org/?255991
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