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Subject: Re: [PHP-DEV] static constructor
From: mail@deroetzi.de (Johannes Ott)

Am 12.03.2015 um 18:55 schrieb Rowan Collins:
> Johannes Ott wrote on 12/03/2015 17:05:
>> Am 12.03.2015 um 16:57 schrieb Rowan Collins:
>>> Johannes Ott wrote on 12/03/2015 14:51:
>>>> That is nearly like initializing a class constant, but in my opinion a
>>>> constant should not have a "complex" algorithm (For example conditions
>>>> or read from filesystem). That should be encapsulated inside a proper
>>>> method body.
>>> I agree, but as such, I think that method should be called somewhere by
>>> the code, even if only by a DI container, not happen automagically and
>>> slurp in data from global state.
>>>
>> It is called somewhere in the code namely inside the static
>> constructor :D
> 
> What I meant is that it is not executed by any piece of code the user
> writes, but directly by the engine based on a magic hook.
> 

Yes but thats why it is called magic method, isn't it ;) No serious if
it is clearly defined what the magic method __static() does and when it
is invoked, it should be okay. All of the magic methods are doing like this.

>>> Incidentally, note that a recent RFC to add the ability to declare a
>>> class as static failed by 12 votes to 5 -
>>> https://wiki.php.net/rfc/abstract_final_class - and much of the
>>> discussion was around static implementations being generally inferior to
>>> instances, so I'm not alone in challenging designs that rely on them.
>>>
>> I will check the rfc later but "static class" sounds strange.

I had time to read the linked rfc now. If I understand it right that rfc
Means a Util-class-pattern for util-classes which should not be
extendable. I don't see the sense of that now, why I util class with
only static methods which typically is defined as abstract should not be
extendable by other, I cannot remember to have this use cased in my 15
years of OOP-programming but okay maybe there are such use cases. But my
proposal is another one see my next comment on your comment below.

> 
> Basically, all your examples imply classes that consist only of static
> members - they're not using static helpers to create instances, they're
> using them *instead of* instances. This was what was mean by "static
> class" in that proposal. Personally, I was in favour of that, since I
> think such classes do exist, and a syntax for declaring them would be
> useful, but the most common argument against was that we should be
> finding ways for people to not need such classes, rather than supporting
> them better. This proposal sounds like it's adding facilities to classes
> that belong on objects, or ... somewhere else.
> 

Okay thats a point I have to clearify I see, maybe my examples where to
much shorten by me. In my examples I'm showing only the initialize parts
of the classes, the initialized properties are used all over the class
in static as well in non-static context.

For use case 1 the LogAdapter for example is a singleton instance per
class, that's why in my understanding of dependcy Injection it is not
working with it (correct me please if I'm wrong). And this singleton is
used to log in all methods of the class/object.

Surely I would be able to get the specializied Singleton instance with
doing some code like the following two examples:

Example 1 (As I already would be prefered solution for me if I use the
Logger only in a few of the methods and not in the majority of it):

class A {

   private static $LOG;

   private static function initLogger() {
      if (self::$LOG = null) {
          self::$LOG = LogAdapter::getLogger(self::class);
      }
   }

   public static function a() {
      self::initLogger();

      self::$LOG->debug();
      ....
      self::$LOG->error();
   }

   public function b() {
      self::initLogger();

      ...
      self::$LOG->error();
   }

   ...

}

or Example 2: (which is in my opinion really hard to read and to much to
write)

class A {

   public static function a() {
      LogAdapter::getLogger(self::class)->debug();
      ....
      LogAdapter::getLogger(self::class)->error();
   }

   public function b() {
      ...
      LogAdapter::getLogger(self::class)->error();
   }

   ...

}

With my solution of a static constructor it would look like this.

class A {

   private static $LOG;

   private static function __static() {
      self::$LOG = LogAdapter::getLogger(self::class);
   }

   public static function a() {
      self::$LOG->debug();
      ....
      self::$LOG->error();
   }

   public function b() {
      ...
      self::$LOG->error();
   }

   ...

}

On huge classes with 10 or more methods all using the LOG reference this
is in my opinion the cleanest and shortest solution.

I hope I could make the example more clear?! If you need more examples
please let me know.

Regards
-- 
DerOetzi