Re: Object constructors/destructors

From	Jerry Stuckle <jstucklex@attglobal.net>
Newsgroups	comp.lang.php
Subject	Re: Object constructors/destructors
Date	2014-02-25 21:08 -0500
Organization	A noiseless patient Spider
Message-ID	<lejiap$v6d$1@dont-email.me> (permalink)
References	(15 earlier) <530d08cd$0$9523$9b4e6d93@newsspool1.arcor-online.net> <lej25h$6gs$1@dont-email.me> <530d1140$0$9522$9b4e6d93@newsspool1.arcor-online.net> <lej3sh$gmp$1@dont-email.me> <530d24cc$0$9525$9b4e6d93@newsspool1.arcor-online.net>

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On 2/25/2014 6:18 PM, Christoph Michael Becker wrote:
> Jerry Stuckle wrote:
>
>> On 2/25/2014 4:55 PM, Christoph Michael Becker wrote:
>>> Jerry Stuckle wrote:
>>>
>>>> On 2/25/2014 4:19 PM, Christoph Michael Becker wrote:
>>>>> Jerry Stuckle wrote:
>>>>>
>>>>>> On 2/25/2014 2:19 PM, Christoph Michael Becker wrote:
>>>>>>> Jerry Stuckle wrote:
>>>>>>>
>>>>>>>> I have my own problems with PHP - for instance, it is entirely
>>>>>>>> possible
>>>>>>>> to create an object without calling a constructor - a violation
>>>>>>>> of OO
>>>>>>>> principles.  But I work around it.
>>>>>>>
>>>>>>> How is it possible to create an object without its constructor (if
>>>>>>> defined) being called?
>>>>>>>
>>>>>>
>>>>>> Load the object from the $_SESSION.  The constructor will not be
>>>>>> called.
>>>>>>
>>>>>> However, the constructor is called when the original object was
>>>>>> created,
>>>>>> and the destructor called when the original object goes out of scope.
>>>>>> The destructor is also called when the object loaded from the
>>>>>> $_SESSION
>>>>>> goes out of scope.
>>>>>>
>>>>>> The result is one constructor call and two destructor calls.  A
>>>>>> violation of OO principles.
>>>>>
>>>>> Um, I'm not sure whether this is a violation of OOP principles.
>>>>> Storing
>>>>> an object in the session requires serialization of the object, what is
>>>>> somewhat comparable to cloning an object.  So actually, you're not
>>>>> working with the *same* object.
>>>>>
>>>>> Anyway, you can work around these issues by using the magic methods
>>>>> __sleep() and __wakeup(), as you probably know. :)
>>>>>
>>>>
>>>> Yes, it is a violation.  When the script starts, the object is
>>>> serialized in the $_SESSION.  But it does not exist in the script.
>>>> Creating it requires a constructor call.
>>>
>>> It requires the object to be created in memory somehow, but the defined
>>> constructor function is not called in this case.
>>>
>>
>> Which is a violation of OO principles.
>>
>>>>                                             OO principles require exactly
>>>> one constructor call and one destructor call for every object created.
>>>> Note these may be explicit or implicit, and the functions may be noops,
>>>> but the calls must still be made.
>>>
>>> When you're cloning an object, its constructor will not be called either.
>>>
>>
>> It is in every other language.  For instance, in Java, clone() acts like
>> a copy constructor.  C++ doesn't have a clone() method, but it does have
>> a copy constructor.
>
> Isn't the copy constructor called on other occassions as the normal
> constructor?
>

A copy constructor is a constructor.  It can be called, or another one 
can be called.

> If so, then PHP doesn't handle that too different.  While
> __constructor() would be the counterpart of a normal constructor,
> __clone() would be the counterpart of a copy constructor.
>

__clone() is not called, either.

>>>>                                     That is not the case here; you get
>>>> one constructor call and two destructor calls.
>>>
>>> I firmly believe that it wouldn't make sense to call a (user-defined)
>>> constructor when unserializing or cloning an object.  A constructor
>>> usually serves to initialize an object -- what already had happened in
>>> both cases.
>>>
>>
>> It makes perfect sense.  Not everything is necessarily valid in the new
>> object.  For instance, a logging object may require opening the log
>> file.  There are many instances where a resource is no longer available
>> and needs to be recreated.
>
> Therefore there are __sleep() and wakeup().  In __sleep() you can close
> the log file (if it's still open), and in __wakeup() you can open it again.
>

Which have nothing to do with construction/destruction.

> Anyway, consider the following snippet:
>
>      <?php
>
>      class Foo {
>          function __construct() {
>              $this->bar = 'foo';
>          }
>          function setBar($bar) {
>              $this->bar = $bar;
>          }
>      }
>
>      $foo = new Foo();
>      $foo->setBar('bar');
>      $bar = unserialize(serialize($foo));
>      echo $bar->bar;
>
> What output would you expect?
>

$bar is a new Foo object, so I would expect a constructor for class Foo 
to be called for object $bar.  That is how it would work in any true OO 
language.

>> PHP's method is only a shallow copy.  Copy constructors and the like
>> were created when a deep copy is required (quite often in other languages).
>
> You can force a deep copy yourself by respectively defining __clone().
>

__clone() is not called when initializing from a $_SESSION value.

>>>> I know of no other OO language which would allow this.
>>>
>>> Others may.
>>>
>>
>> None that I know of.  Please name one.
>
> Obviously, I was too terse here.  I meant: "I can't name one, but others
> may be able to name one."
>

You can't name one because true OO languages do it right.

-- 
==================
Remove the "x" from my email address
Jerry Stuckle
jstucklex@attglobal.net
==================

Thread

Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-23 18:03 +0100
  Re: Operator precedence GS <nomail@nospam.org.invalid> - 2014-02-23 19:42 +0000
    Re: Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-23 21:23 +0100
    Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-23 16:34 -0500
      Re: Operator precedence Richard Damon <Richard@Damon-Family.org> - 2014-02-23 18:36 -0500
        Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-23 21:09 -0500
          Re: Operator precedence Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-02-24 04:49 +0000
            Re: Operator precedence Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-24 12:56 +0100
              Re: Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-24 17:38 +0100
              Re: Operator precedence Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-02-24 21:25 +0000
                Re: Operator precedence Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-25 00:38 +0100
                Re: Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-25 01:07 +0100
                Re: Operator precedence Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-25 01:37 +0100
                Re: Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-25 02:12 +0100
                Re: Operator precedence Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-25 03:29 +0100
                Re: Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-25 19:41 +0100
                Re: Operator precedence Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-25 19:55 +0100
                Re: Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-25 21:36 +0100
                Re: Operator precedence Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-02-25 03:08 +0000
                Re: Operator precedence Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-25 04:17 +0100
                Re: Operator precedence Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-02-25 04:45 +0000
                Re: Operator precedence GS <nomail@nospam.org.invalid> - 2014-02-25 21:45 +0000
            Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-24 07:00 -0500
              Re: Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-24 18:11 +0100
                Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-24 14:27 -0500
                Re: Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-25 01:25 +0100
                Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-24 20:40 -0500
              Re: Operator precedence Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-02-24 21:23 +0000
                Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-24 16:45 -0500
                Re: Operator precedence Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-02-25 04:32 +0000
                Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-24 23:47 -0500
                Re: Operator precedence Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-02-25 16:56 +0000
                Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-25 13:59 -0500
                Re: Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-25 20:19 +0100
                Re: Operator precedence Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-25 20:43 +0100
                Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-25 16:02 -0500
                Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-25 16:01 -0500
                Object constructors/destructors (was: Operator precedence) Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-25 22:19 +0100
                Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-25 16:32 -0500
                Re: Object constructors/destructors Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-25 22:55 +0100
                Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-25 17:01 -0500
                Re: Object constructors/destructors Adam Harvey <usenet@adamharvey.name> - 2014-02-25 23:22 +0000
                Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-25 21:10 -0500
                Re: Object constructors/destructors Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-26 21:10 +0100
                Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-26 16:01 -0500
                Re: Object constructors/destructors Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-26 22:59 +0100
                Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-26 17:19 -0500
                Re: Object constructors/destructors Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-26 23:39 +0100
                Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-26 22:30 -0500
                Re: Object constructors/destructors Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-27 18:28 +0100
                Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-27 16:09 -0500
                Re: Object constructors/destructors Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-28 14:52 +0100
                Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-28 09:08 -0500
                Re: Object constructors/destructors Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-28 16:52 +0100
                Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-28 11:03 -0500
                Re: Object constructors/destructors Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-27 01:00 +0100
                Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-26 22:39 -0500
                Re: Object constructors/destructors Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-27 18:29 +0100
                Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-27 16:14 -0500
                Re: Object constructors/destructors Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-26 00:18 +0100
                Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-25 21:08 -0500
                Re: Object constructors/destructors Richard Damon <Richard@Damon-Family.org> - 2014-02-26 07:50 -0500
                Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-26 08:44 -0500
                Re: Object constructors/destructors Richard Damon <Richard@Damon-Family.org> - 2014-02-26 23:49 -0500
                Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-27 08:25 -0500
                Re: Object constructors/destructors Richard Damon <Richard@Damon-Family.org> - 2014-03-01 12:56 -0500
                Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-03-01 14:22 -0500
                Re: Object constructors/destructors Richard Damon <Richard@Damon-Family.org> - 2014-03-02 14:28 -0500
                Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-03-02 15:42 -0500
                Re: Object constructors/destructors Richard Damon <Richard@Damon-Family.org> - 2014-03-02 17:14 -0500
                Re: Object constructors/destructors Jerry Stuckle <jstucklex@attglobal.net> - 2014-03-02 17:48 -0500
                Re: Object constructors/destructors Tim Streater <timstreater@greenbee.net> - 2014-03-02 23:05 +0000
                Re: Operator precedence Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-02-25 21:08 +0000
                Re: Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-25 22:29 +0100
                Re: Operator precedence Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-02-25 23:15 +0000
              Re: Operator precedence Richard Damon <Richard@Damon-Family.org> - 2014-02-24 22:41 -0500
                Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-02-24 23:59 -0500
                Re: Operator precedence Richard Damon <Richard@Damon-Family.org> - 2014-03-01 13:39 -0500
                Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-03-01 14:29 -0500
                Re: Operator precedence Richard Damon <Richard@Damon-Family.org> - 2014-03-02 15:22 -0500
                Re: Operator precedence Jerry Stuckle <jstucklex@attglobal.net> - 2014-03-02 15:49 -0500
                Re: Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-25 19:15 +0100
  Re: Operator precedence Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-02-23 20:56 +0000
    Re: Operator precedence Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-24 14:28 +0100

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