Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:33387
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain gmail.com designates 64.233.182.187 as permitted sender)
DomainKey-Status: bad
DomainKey-Signature: a=rsa-sha1; c=nofws;
        d=gmail.com; s=beta;
        h=received:from:to:cc:references:in-reply-to:subject:date:mime-version:content-type:content-transfer-encoding:x-mailer:thread-index:content-language:message-id;
        b=IzYIFGg8b3/7rcKQmqHOaaYch/Dm1BtreL7tjlsjQhxvZEEWOvu6Yd8ej8SP+o9DxiwYttkoNjag36Q6ewWFUoMwWkZDaxPeOArC9a0dfqeEExMPd7oNBlaVy4Gb5zEU8UwR5Z9MEf/On6EC2v2Kqp6atRzsjQFAyDT3exD9Rgg=
To: <RQuadling@GoogleMail.com>
Cc: "'PHP Developers Mailing List'" <internals@lists.php.net>,
	<helly@php.net>
References: <4740C654.3020302@digitalsandwich.com> <4741DC81.6000506@zend.com>	 <4741D574.2020800@digitalsandwich.com> <474247A2.5050301@zend.com>	 <4741D9D1.6030106@digitalsandwich.com> <47424B4F.2@zend.com>	 <4743CED7.5050402@avalon.aut.bme.hu>	 <a2b4d2820711221229o2debeb30leb4679e316656ecc@mail.gmail.com>	 <a2b4d2820711221240y3742606ar4cc6a2e84d6fda07@mail.gmail.com>	 <10845a340711230118t6c19243cg812f22858e3a3c75@mail.gmail.com> <10845a340711230121j1e06040bw15953d02330b622@mail.gmail.com>
In-Reply-To: <10845a340711230121j1e06040bw15953d02330b622@mail.gmail.com>
Date: Fri, 23 Nov 2007 10:53:11 +0100
MIME-Version: 1.0
Content-Type: text/plain;
	charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Thread-Index: AcgtskhFZEZUXiMER1C1PdvEYf3IywAAdz8g
Content-Language: de
Message-ID: <4746a3f8.12975e0a.018f.3392@mx.google.com>
Subject: RE: [PHP-DEV] late static binding php6
From: marco.kaiser@gmail.com ("Marco Kaiser")

Hi Richard,

the problem is this:

<?php
abstract class singleton
{
    static protected $_instance;
   =20
	static final public function getInstance()
	{
	    $caller =3D get_called_class();
	    if (!static::$_instance instanceof $caller) {
	        echo "NEW INSTANCE\n";
            static::$_instance =3D new $caller;
	    }

	    return static::$_instance;
	}
}

class foo extends singleton {
	static protected $_instance;
}

class bar extends singleton {
	static protected $_instance;
}

var_dump(foo::getInstance());
var_dump(bar::getInstance());
var_dump(foo::getInstance());
var_dump(bar::getInstance());
?>

NEW INSTANCE
object(foo)#1 (0) {
}
NEW INSTANCE
object(bar)#2 (0) {
}
object(foo)#1 (0) {
}
object(bar)#2 (0) {
}

This means i just called once the constructor for the singleton abstract =
for every main class (foo, bar)
But if you remove the static member $_instance from the foo and bar =
class you get this result:

NEW INSTANCE
object(foo)#1 (0) {
}
NEW INSTANCE
object(bar)#2 (0) {
}
NEW INSTANCE
object(foo)#1 (0) {
}
NEW INSTANCE
object(bar)#2 (0) {
}

You see that the constructor is called every time if you use more than 1 =
singleton class during script execution.
The problem is that the property isnt really inherited by the foo and =
bar class.

My idea or a possible solution would be to allow the definition of =
correct inheritance of the $_instance property or
to show me a way to set a static property dynamicly in the caller class.
Maybe Andi or Markus can explain this a bit more why this isnt possible. =
:)

-- Marco

> -----Original Message-----
> From: Richard Quadling [mailto:rquadling@googlemail.com]
> Sent: Friday, November 23, 2007 10:22 AM
> To: Marco Kaiser
> Cc: PHP Developers Mailing List
> Subject: Re: [PHP-DEV] late static binding php6
>=20
> On 23/11/2007, Richard Quadling <rquadling@googlemail.com> wrote:
> > On 22/11/2007, Marco Kaiser <marco.kaiser@gmail.com> wrote:
> > > Hi again,
> > >
> > > to explain the main idea a bit more, the code below work and moves
> the
> > > main getInstance function from the class and its possible to
> abstract
> > > this.
> > > it would be cool to get the protected property also into the
> abstract
> > > class. Any idea or maybe a solution in the near future?
> > >
> > > <?php
> > > abstract class singleton
> > > {
> > >         static public function getInstance()
> > >         {
> > >             $caller =3D get_called_class();
> > >             if (!static::$_instance instanceof $caller) {
> > >             static::$_instance =3D new $caller;
> > >             }
> > >
> > >             return static::$_instance;
> > >         }
> > > }
> > >
> > > class foo extends singleton {
> > >         static protected $_instance =3D null;
> > > }
> > >
> > > class bar extends singleton {
> > >         static protected $_instance =3D null;
> > > }
> > >
> > > var_dump(foo::getInstance());
> > > var_dump(bar::getInstance());
> > > var_dump(foo::getInstance());
> > > var_dump(bar::getInstance());
> > > ?>
> > >
> > > On Nov 22, 2007 9:29 PM, Marco Kaiser <marco.kaiser@gmail.com>
> wrote:
> > > > Hi List,
> > > >
> > > > just to drop my note here, i asked (i think) 2 years ago for =
such
> a
> > > > feature to automate my singleton pattern. Not with late static
> > > > bindings this is possible.
> > > >
> > > > <?php
> > > > class singleton
> > > > {
> > > >         static protected $_instance =3D null;
> > > >
> > > >         static public function getInstance()
> > > >         {
> > > >             $caller =3D get_called_class();
> > > >             if (!static::$_instance instanceof $caller) {
> > > >             static::$_instance =3D new $caller;
> > > >             }
> > > >
> > > >             return static::$_instance;
> > > >         }
> > > > }
> > > >
> > > > class foo extends singleton
> > > > {
> > > > }
> > > >
> > > > var_dump(foo::getInstance());
> > > > var_dump(foo::getInstance());
> > > > ?>
> > > >
> > > > i think this will also drop much redundant code from some
> frameworks. :)
> > > > So this is one of my examples that helps much.
> > > >
> > > >
> > > > --
> > > > Marco Kaiser
> > > >
> > >
> > >
> > >
> > > --
> > > Marco Kaiser
> >
> > <?php
> > abstract class singleton
> > {
> >        static protected $_instance =3D null;
> >        static public function getInstance()
> >        {
> >            $caller =3D get_called_class();
> >            if (!static::$_instance instanceof $caller) {
> >            static::$_instance =3D new $caller;
> >            }
> >
> >            return static::$_instance;
> >        }
> > }
> >
> > class foo extends singleton {
> > }
> >
> > class bar extends singleton {
> > }
> >
> > var_dump(foo::getInstance());
> > var_dump(bar::getInstance());
> > var_dump(foo::getInstance());
> > var_dump(bar::getInstance());
> > ?>
> >
> > returns ...
> >
> > object(foo)#1 (0) {
> > }
> > object(bar)#2 (0) {
> > }
> > object(foo)#1 (0) {
> > }
> > object(bar)#2 (0) {
> > }
> >
> > in PHP 5.3.0-dev (cli) (built: Nov 20 2007 08:19:12)
> >
> > I think this is great! Well done everyone. Unless I've completely
> > missed the point.
>=20
> Also, you can make the getInstance() method final so it cannot be
> overridden in sub-classes...
>=20
> <?php
> abstract class singleton
> {
>        static protected $_instance =3D null;
>        static final public function getInstance()
>        {
>            $caller =3D get_called_class();
>            if (!static::$_instance instanceof $caller) {
>            static::$_instance =3D new $caller;
>            }
>=20
>            return static::$_instance;
>        }
> }
>=20
> class foo extends singleton {
> 	public function getInstance() { return 'foobar'; }
> }
>=20
> class bar extends singleton {
> }
>=20
> var_dump(foo::getInstance());
> var_dump(bar::getInstance());
> var_dump(foo::getInstance());
> var_dump(bar::getInstance());
> ?>
>=20
> returns ...
>=20
> Fatal error: Cannot override final method singleton::getInstance() in
> C:\sing.php on line 18
>=20
> So, a very useful addition to the language.
>=20
> --
> -----
> Richard Quadling
> Zend Certified Engineer :
> http://zend.com/zce.php?c=3DZEND002498&r=3D213474731
> "Standing on the shoulders of some very clever giants!"