Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:64126
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain gmail.com designates 209.85.215.170 as permitted sender)
MIME-Version: 1.0
Sender: sebastian.krebs.berlin@gmail.com
Date: Sat, 1 Dec 2012 13:34:58 +0100
Message-ID: <CALtuQzA0M80O3P3yrOqn-hWFk5+uCYoM+8rAqNK-f5e8CUwXyg@mail.gmail.com>
To: PHP internals list <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=047d7b622820884dbf04cfc9be12
Subject: Abstract properties
From: krebs.seb@gmail.com (Sebastian Krebs)

--047d7b622820884dbf04cfc9be12
Content-Type: text/plain; charset=ISO-8859-1

Hi,

Don't want to start a big discussion, but is there a concrete reason, why
abstract properties (or "a kind of abstract") are not supported? I've
learned, that "an interface [the concept, not the implementations within a
language] is the sum of all accessible (--> public) methods and
properties", what as far as I understand means, that properties could (and
should) be defineable in concrete interfaces too

interface Queue {
  public function enqueue($value);
  public function dequeue();
  public $top;
}
// or
abstract class Queue {
  abstract public function enqueue($value);
  abstract public function dequeue();
  abstract public $top;
}

Of course in the second example the "abstract" is kind of useless, but it's
for illustration. I've seen some cases (for example the example above),
where it would be useful to define properties in interfaces, but instead I
was forced to (in my eyes) misuse [1] methods. Right now I cannot safely
write somethig like

/**
 * Must have a $top property
 */
interface Queue {
  public function enqueue($value);
  public function dequeue();
}

function foo(Queue $q) {
  doSomethingWithTop($q->top);
}

Because I can never ensure, that $top exists. I always have to work with
isset() here (or of course I use a getter, as mentioned earlier), what
takes a little bit from the "usefulness" of interfaces ^^ The interface
feels incomplete.

Would like to hear some opinions, or maybe a summary of earlier discussions
about this topic :)

Regards,
Sebastian




[1] I've also learned, that methods define behaviour and properties define
the state. "$top" in the example is part of the state, thus calling a
method to fetch the state feels wrong/like a hack (thats btw my opinion
about getters/setters too; just to create a bridge to other concepts ;)).

-- 
github.com/KingCrunch

--047d7b622820884dbf04cfc9be12--