Chris W. Parker wrote:
> Hello,
>
> I'm working on a project now and I'd like to get some feedback on how to
> implement a proper class (or two).
>
> This is an application that records an employee's used vacation time.
> There are two tables: (1) events, (2) users.
>
> Users:
>
> id (int)
> name (varchar)
> email (varchar)
> balance (mediumint, stored in seconds) // this is the balance for
> // the user after all events
> // have been accounted for.
> accrual (smallint, stored in seconds)
> is_manager (bool)
>
> Events:
>
> id (int)
> uid (int, users.id)
> date (date)
> duration (smallint, stored in seconds)
> balance (smallint, stored in seconds) // this is the balance for
> // the user at the time the
> // event was added.
> created (datetime)
>
>
> Currently I have just one class called User that looks like this:
>
>
> (I'm dealing with PHP4.)
>
> class User
> {
> var id;
> var name;
> var email;
> var balance;
> var accrual;
> var is_manager;
>
> function User($user_id)
> {
> $this->id = $user_id;
> $this->name = get_name();
> // ...
> $this->accrual = get_accrual();
> }
>
> function get_name()
> {
> // get name from db
> $sql = "...";
>
> $db =& DB::singleton();
> $db->execute($sql);
you probably only want one DB call to
populate the User object with all the relevant
user data at the point where the object is created.
function User($user_id)
{
// check the user id properly?
// see the getEmployee() example below for the
// reason for the array usage
if (is_array($user_id)) {
$this->id = $user_id['id'];
$this->load($user_id);
} else {
$this->id = $user_id;
$this->load();
}
}
function load($data = null)
{
if (!is_array($data) || empty($data)) {
// get user data from db
$sql = "SELECT * FROM users WHERE id={$this->id}";
// error checking?
$db =& DB::singleton();
$db->execute($sql);
$data = $db->getRow();
}
$this->name = $data['name'];
$this->accrual = $data['accrual'];
$this->email = $data['email'];
/// etc
}
>
> function get_email()
> function get_accrual()
> function is_manager()
> {
> // same as above more or less
> }
>
> function get_events()
> {
> // this function gets all the events for
> // the current users and returns them
> // as an array.
> }
>
> function add_event()
> {
> // this function adds a single event for
> // the current user. it also recalculates
> // the 'balance' for each event because
> // of data display requirements.
> }
>
> function del_event($event_id)
> {
> // delete an event from the current user's
> // events list based on $event_id.
> }
> }
>
>
> As I started to write this and use it I get the feeling that there
> should also be an Event class that is extended by the User class. Reason
if you use an Event class then it should just represent an Event (and
a User object would [probably] contain an array of Event objects).
AFAICT there is no good reason to have Event extend User.
> being that each User object is a reference to the currently logged in
> user, not anyone else.
the User class is merely a representation of *a* user - you can
use an instance for the currently logged in user, but that doesn't stop you
from using the same class to model the collection of users that fall under
a given manager.
> But if you're a manager you have the
> responsibility to approve/deny and/or add/delete events for your
> employees.
// you might need to f around with returning references here,
// (I can never quite get that right without a bit of trial and error in php4)
function getEmployees()
{
// consider caching the result?
$emps = array();
if ($this->is_manager) {
// get user data from db
$sql = "SELECT * FROM users WHERE manager_id={$this->id}";
// error checking?
$db =& DB::singleton();
$db->execute($sql);
while ($data = $db->getRow())
$emps[] =& new User($data);
}
return $emps;
}
>
> But with that in mind I've gone from a class that handles the currently
> logged in user to one that handles the currently logged in user plus any
> number of other users.
>
> I guess I'm thinking of this in the same terms as db normalization. Ex:
> I could add an extra price_level column to my products table each time I
> need a new pricing level but it's probably better to create a separate
> table called products_prices. It's slightly more complicated but it
> would allow me to have as many pricing levels as I want without
> modifying my databse or code.
>
>
> I'd appreciate any kind of feedback on this. If I haven't been clear
> with something please let me know.
>
>
>
> Thanks,
> Chris.
>
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