Question

I am going to use singleton classes to manage both DB connections and references to application settings.

It seems a little messy to have to use the following code in every method in order to access the db class.

$db = DB::getInstance();

Is there a more efficient way of going about it?

Any advice appreciated.

Thanks

Answer 1

I often use the Registry pattern, where this behavior occurs as well. I always set a instance variable in the constructor of my models to point to the Registry entry;

class Registry {
    private static $_instance;
    private $_registry;

    private function __construct() {
        $_registry = array();
    }

    public static function getInstance() {
        if (!Registry::$_instance) {
            Registry::$_instance = new Registry();
        }

        return Registry::$_instance;
    }

    public function add($key, &$entry) {
        $this->_registry[$key] = &$entry;
    }

    public function &get($key) {
        return $this->_registry[$key];
    }

    public function has($key) {
        return ($this->get($key) !== null);
    }
}

Model example;

class MyModel {
    private $_db;
    public function __construct() {
        $this->_db = Registry::getInstance()->get('dbKey');
    }

    /* Every function has now access to the DAL */
}

Instantiation example;

$dal = new Db(...);
Registry::getInstance()->add('dbKey', $dal);
...
$model = new MyModel();
$model->doDbStuff();

Another approach is to always pass the reference as a parameter to each constructor.

Of course I only use this behavior when most of the methods in my model use the reference, if only a few (one or two) methods have use of the reference, I call the Registry/Singleton like you showed.