Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:46077
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain gmail.com designates 209.85.220.227 as permitted sender)
DomainKey-Status: bad
DomainKey-Signature: a=rsa-sha1; c=nofws;
        d=gmail.com; s=gamma;
        h=mime-version:in-reply-to:references:date:message-id:subject:from:to
         :content-type:content-transfer-encoding;
        b=xspxjvjmaJGwjGKgngExjGn3e8rUhj9Z+Fd/CAXjkAIE1mM12PDURs2aQDwhXbDqmS
         F1E6GnsYQEPbbRrrw6ElQdQyvsThvnf9XisuqjYsvGY2WLVgNHzq9fNxrKLSNLop207h
         U6/3o9lR3SuVJPTXFLTBOTax4A5zJ1Bx+f6XU=
MIME-Version: 1.0
In-Reply-To: <4B02D7FA.3080206@easyflirt.com>
References: <4B01A4C2.8030602@gmx.net> <4B0273E5.9000606@easyflirt.com>
	 <e2e02fe0911170839n28b8d6ffv962b92386d2db2a6@mail.gmail.com>
	 <4B02D7FA.3080206@easyflirt.com>
Date: Wed, 18 Nov 2009 10:32:00 +0300
Message-ID: <d1d50abe0911172332m6ba7d102k3cf5fe823a5ed83c@mail.gmail.com>
To: internals@lists.php.net
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
Subject: Re: [PHP-DEV] Closures and $this
From: crocodile2u@gmail.com (Victor Bolshov)

Hi.

Personally, I beleive that (A) approach is the best: "bind $this to
the object scope at creation" and never change it, issue error when
$this is used where not available. It also seems to me like this way
it could be implemented with better performance, am I right?

Dynamically changing $this introduces confusion. You can use
$this->foo or $this->bar() inside a closure, but when $this
dynamically changes - you cannot be sure that "foo" property or "bar"
method is still there. Furthermore, dynamic approach introduces even
more mess when thinking about availability of private/protected class
members.

Consider this code:

class Foo {
  private $closure;
  function __construct()
  {
    /* It seems natural to me that, doing this assignment from within the c=
lass,
       one can use private members inside the closure */
    $this->closure =3D function() { $this->privateMethod(); };
  }
  function setClosure($closure)
  {
    $this->closure =3D $closure;
  }
  function getClosure()
  {
    return $this->closure;
  }
}

$foo =3D new Foo();
$foo->getClosure()->__invoke();// #CALL-1
$foo->setClosure(function() {
  /*
  But is it good to use private members here? It seems like it would
break encapsulation,
  and the information that the class was designed to hide - is now
made available in public access,
  although indirect.
  */
  $this->privateMethod();
});
$foo->getClosure()->__invoke();// #CALL-2

In the end, I would like PHP to issue error when $this is used in
#CALL-2 but to continue working on #CALL-1.

The (A) approach seems to me more predictable, more simple, it has
less information the developer needs to keep in mind when using
closures.

2009/11/17 Mathieu Suen <mathieu.suen@easyflirt.com>:
> Chris Stockton a =E9crit :
>>
>> Hello,
>>
>> On Tue, Nov 17, 2009 at 2:59 AM, Mathieu Suen
>> <mathieu.suen@easyflirt.com> wrote:
>>>
>>> Christian Seiler a =E9crit :
>>>>
>>>> Hi,
>>>>
>>>> since a few months have passed since the last discussion on this topic
>>>> and perhaps people had time to gather some experience with the current
>>>> closure implementation in PHP 5.3 I'd like to restart the debate on
>>>> $this in closures and object extension.
>>
>> I believe that (D) wins my vote, and it convinces me twice. Once
>> because I believe it is the most intuitive for users (A), and twice
>> because I believe it is also the most useful (C) for users. In my
>> opinion It seems the most "PHP" way.
>>
>> -Chris
>>
>
> (D) is quite inconstant:
>
> $block =3D $foo->closur;
>
> $foo->closur();
> $block();
>
> This would produce 2 different output.
> For (C) here is my objection:
>
> Suppose that we are in a MVC pattern.
> In a controller on could do:
>
> $model->onFailDo(function () {$this->reportError()});
> $model->save();
>
>
> In the model side:
>
> public function onFailDo($block)
> {
> =A0 =A0 =A0 =A0$this->signalFailure =3D $block
> }
>
> public function save()
> {
> =A0 =A0 =A0 =A0//... Something wrong happen
> =A0 =A0 =A0 =A0return $this->signalFailure();
> }
>
> If you dynamically bind the $this you are obliged to treat the error
> reporting in the model which is not a good idea. Even worst you can't eve=
n
> catch up the error in the controller.
> It also mean that the closure is getting tightly coupled with anyone who =
is
> using it. And passing closure to different object is like spreading
> dependency over all the system.
>
> -- Mathieu Suen
>
> --
> PHP Internals - PHP Runtime Development Mailing List
> To unsubscribe, visit: http://www.php.net/unsub.php
>
>

--=20
Regards,
Victor