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Date: Sat, 11 Dec 2010 17:47:03 +0100
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To: "internals@lists.php.net Development" <internals@lists.php.net>
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Subject: Traits and Properties
From: php@stefan-marr.de (Stefan Marr)

Hi:

Traits do not provide any special provisioning for handling properties, =
especially, there is no language solution for handling colliding =
property names.
The current solution/idiom for handling state safely in a trait is to =
use either abstract set/get methods or an abstract get that returns a =
reference to the property in the class.

However, at the moment it is possible to define properties in a trait:

trait Foo {
 private $a;
 public  $foo;
}

For the moment, that information is completely ignored, thus:

class Bar {
 use Foo;
}
property_exists('Bar', 'a') =3D=3D=3D false


Well, and that is a rather inconsistent status-quo.

I would like to have that fixed in one or another way.

One possibility would be to forbid property definition in a trait =
altogether.
That reduces a bit the possibility to have wrong expectations about =
properties, however, the dynamic property creation is still possible.

Another way would be to merge the properties in the composing class.
The question here would be how to treat visibility modifiers: how to =
merge public and private, should it result in public, or private?
And, to discorage users to go this way, should there be a STRICT notice? =
Options here are a notice whenever a property is defined in a trait, or =
whenever properties are silently merged.


Comments very welcome.

Thanks
Stefan

--=20
Stefan Marr
Software Languages Lab
Vrije Universiteit Brussel
Pleinlaan 2 / B-1050 Brussels / Belgium
http://soft.vub.ac.be/~smarr
Phone: +32 2 629 2974
Fax:   +32 2 629 3525