The simplest way to solve this problem is as follows:
- Have your Customer class hold only attributes for a customer. This class
would only have getter and setter methods. In the Java world, this is
referred to as a JavaBean.
- Then, have a DAO class that does your data access functions.
Here is a sample DAO class:
class CustomerDAO {
function getCustomer(..) {
...
//return a customer
}
function getCustomers(..) {
...
// return a collection of customers
}
function saveCustomer(..) {
...
}
}
Hope this helps.
--
Anas Mughal
On 9/19/05, Chris W. Parker <cparker@xxxxxxxxxxxx> wrote:
>
> 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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>
>
--
Anas Mughal
