Suggestions for class design

["Chris W. Parker" <cparker@xxxxxxxxxxxx>]

Hello,

Every time I write some classes I always come across the same
fundamental problem that I haven't figured out how to solve/approach
yet. I'm not exactly sure how to put it into words simply but here
goes...

Let's take for example a class called 'Customer' that (obviously)
manipulates customers in the database. Here is a very basic Customer
class. (Data validation and the like are left out for brevity.)

class Customer
{
	var $id;
	var $name;

	function add_customer()
	{
		// create sql statement
		$sql = "INSERT INTO ...";

		// create db connection
		$db =& DB::singleton();

		// execute SQL
		$db->execute($sql);
	}

	function delete_customer()
	{
		// create sql statement
		$sql = "DELETE FROM ...";

		// create db connection
		$db =& DB::singleton();

		// execute SQL
		$db->execute($sql);
	}

	function get_customer()
	{
		// create sql statement
		$sql = "SELECT ... FROM ...";

		// create db connection
		$db =& DB::singleton();

		// execute SQL
		$customer = $db->execute($sql);

		// populate object variables
		$this->id   = $customer['id'];
		$this->name = $customer['name'];
	}
}

(Unless I've already got some major design flaws I think we should be
good to go.)

Where I get tripped up is when I realize I'll need to at some point get
more than one customer at a time and thus I want to add a method called
'get_customers()'.

Since an object should be a single instance of something (e.g. ONE
customer) how do I justify adding the method 'get_customers()'? Or
better yer, how do I properly add a method like that? (A method where
instead of using a SQL statement to return ONE customer's data I instead
return a record set with more than one customer.)

The class in its current state can't handle data like that so I have to
then rethink the design and a new object variable called $customers
where I store the record set that is in return accessed directly by the
calling page itself.

With the way I'm working with these objects now they seem less like
objects and more like an organized collection of functions.


I'd appreciate some actual code recommendations as I have a hard time
understanding the abstract descriptions of how objects should work and
be designed.



Thanks,
Chris.

Thanks!
Chris.

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