Using static method to create objects

captainmerton · 06-01-2009, 06:34 PM

Wonder if anyone can help me with the syntax for this. I have created a class called Collective and with that class a public static method called getInstance which reads several rows from a mysql table and creates an object of class Collective for every row read. I;m not getting any major syntax errors when i run this but it just isnt working well the db call is working and returning what i expect but the object creation but isnt. Any advice? (PS - I'm just passing in joebloggs to test the class and i'm getting rows back from the database so no problem there).

Client Code:

PHP Code:


			
require_once('./lib/collective.class.php');

$coltable = Collective::getInstance('joebloggs');

Collective Class code:

PHP Code:


			
    class Collective {

        /* Custom Error Message for a field left blank */

        const ERROR_NO_COLLECTIVES = "Error - No Collectives Found!";



        /* The collective id */

        private $colid;

        

        /* The collective name */

        private $colname;



        /* The collective name */

        private $username;



        /* Instance of Object */

        private static $instance;





        /* Contructor */

        private function _contruct($colid, $colname) { 

        $this->colid    = $colid;

        $this->colname    = $colname;

        $this->dispColid();

        $this->dispColname();    

        }

    

        /* Create Object Instances */

        public static function getInstance($username) {

            $query = "select colid, colname from collective where username = '$username'";



            $result = mysql_query($query) OR die('Cannot perform getInstance query!');    



                if (mysql_num_rows($result) == 0) {        

                    throw new Exception(Collective::ERROR_NO_COLLECTIVES);

                }

                else {

                    while($row = mysql_fetch_array($result))

                    {

                    self::$instance = new Collective($row['colid'],$row['colname']);

                    }

                }

        }

    

        /* Return the collective id */

        public function getColid() {

            return $this->colid;

        }

    

        /* Return the collective name */

        public function getColname() {

            return $this->colname;

        }



        /* Return username associated with the collective */

        public function getUsername() {

            return $this->username;

        }



        /* Print the collective id */

        public function dispColid() {

            print $this->colid;

        }

    

        /* Print the collective name */

        public function dispColname() {

            print $this->colname;

        }

            

    }

gilbertoalbino · 06-03-2009, 02:25 AM

Hi, dear Captain Merton!

I've run some tests on your script and have little to say!

Your code is okay, the SingleTon Pattern is correct,
but you typed the Constructor wrong:

Code:

private function _contruct($colid, $colname)

The correct is:

Code:

private function __construct($colid, $colname)

Just it! Congratulation on your way with Design Patterns!

captainmerton · 06-03-2009, 08:27 AM

Brilliant thanks Gilberto. In all my testing I could tell that it was not getting to the construct function but was throwing no error as i assume it was simply treating it as another class method. But I didnt ever consider the spelling being wrong. Thanks for taking the time to look it over. Cheers.

gilbertoalbino · 06-03-2009, 01:30 PM

You're welcome!
Well, I did every possible test and, in fact, finding the spelling error was the last thing I did!