Extend abstract singleton class

user_53948 0
Viewed 16624

If you had a factory class that creates new objects of some kind, and that factroy class is a singleton, like this:

class Database_Factory extends Base_Factory {
    private static $factory;
    private $objects = array();

    public function __get($profile) {
        // check for object and return it if it's created before
    }

    public static function getInstance(){
        if (!self::$factory)
            self::$factory = new self();
        return self::$factory;
    }
}

The same code repeats anytime where some object needs it's own factory. So i decided to make this factory class abstract and implement only specific routines for each factory. But PHP does not allow to instantiate abstract class.

abstract class Base_Factory {
    public static function getInstance(){
        if (!self::$factory)
            self::$factory = new self();
        return self::$factory;
    }
}

Fatal error: Cannot instantiate abstract class Base_Factory

What would you do?

abstract-class singleton php
6 Answers

PHP 5.3+

abstract class Singleton
{
    /**
     * Instance
     *
     * @var Singleton
     */
    protected static $_instance;

    /**
     * Constructor
     *
     * @return void
     */
    protected function __construct() {}

    /**
     * Get instance
     *
     * @return Singleton
     */
    public final static function getInstance() {
        if (null === static::$_instance) {
            static::$_instance = new static();
        }

        return static::$_instance;
    }
}
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