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Re: Object constructors/destructors [message #185110 is a reply to message #185106]

Wed, 26 February 2014 21:59

Christoph Michael Bec
Messages: 207
Registered: June 2013

Karma:

Senior Member

Jerry Stuckle wrote:

> On 2/26/2014 3:10 PM, Christoph Michael Becker wrote:
>> Jerry Stuckle wrote:
>>
>>> On 2/25/2014 6:22 PM, Adam Harvey wrote:
>>>> On Tue, 25 Feb 2014 17:01:52 -0500, Jerry Stuckle wrote:
>>>> > On 2/25/2014 4:55 PM, Christoph Michael Becker wrote:
>>>> >> 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.
>>>>
>>>> Indeed, which is why PHP provides the Serializable interface (and,
>>>> for BC
>>>> reasons, also __sleep and __wakeup) to allow those sorts of
>>>> reinitialisation tasks.
>>>>
>>>> I agree with Christoph: since the object is already instantiated, it
>>>> doesn't logically make sense to call the constructor once again.
>>>>
>>>
>>> But the object is NOT instantiated. It was at one time, then destroyed.
>>> When the new script starts, there is no object in existence.
>>>
>>>> >> Jerry Stuckle wrote:
>>>> >>> I know of no other OO language which would allow this.
>>>> >>
>>>> >> Others may.
>>>> >>
>>>> >>
>>>> > None that I know of. Please name one.
>>>>
>>>> Python's pickle operates the same way:
>>>> http://docs.python.org/2/library/pickle.html#object.__getinitargs__
>>>>
>>>> Providing a way to instantiate objects without calling the constructor
>>>> does have valid uses (mostly for testing), which is why PHP 5.4 and
>>>> later
>>>> versions also provide a way to do so via reflection (avoiding the
>>>> unserialize() hack):
>>>> http://php.net/reflectionclass.newinstancewithoutconstructor
>>>>
>>>> Adam
>>>>
>>>
>>> Not knowing Python, I can't say. But if it is a true object, then they
>>> are also violating OO principles.
>>>
>>> OO demands creation of a new object requires a constructor call.
>>> Period.
>>
>> Do you understand, what's the purpose of a constructor? It is there to
>> *initialize* an instance. If there is nothing to initialize, it is not
>> strictly necessary to call any constructor.
>>
>
> Yes, I understand the purpose of a constructor - it looks like much more
> than you do.
>
>> But anyway, unserializing an object is *not* creating a new object.
>> Consider a class man. When a new object is instantiated the constructor
>> is called to initialize the person with respective properties (e.g. age
>> = 0). Later this man goes to sleep (serialize); after he wakes up
>> (unserialize) the constructor is not called again, as this would reset
>> the man to his initial properties, and surely after a good night of
>> sleep one may feel younger, but the age has not been reset.
>>
>
> It is creating a new object. Before unserialize(), the object does not
> exist - only a bunch of data. And that data is NOT an object! You
> cannot call an object method on the data, for instance. It is no
> different than if the data were stored in a file and loaded in Java or
> C++, for instance. To create the object requires a call to a constructor.

If you really need to think this way, just take
Serializable::serialize() resp. __sleep() as a destructor and
Serializable::unserialize() resp. __wakeup() as a constructor.
Actually, the documentation of the Serializable interface explaines it
that way.

>>> If you think otherwise, I suggest you learn more about how OO
>>> is supposed to work. PHP is not a good example.
>>
>> I refrain from commenting this statement.
>>
>
> If you think otherwise, I suggest you learn more about how OO is
> supposed to work. PHP is not a good example.

No comment.

--
Christoph M. Becker

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[Message index]

		Operator precedence By: Christoph Michael Bec on Sun, 23 February 2014 17:03
		Re: Operator precedence By: GS on Sun, 23 February 2014 19:42
		Re: Operator precedence By: Christoph Michael Bec on Sun, 23 February 2014 20:23
		Re: Operator precedence By: Jerry Stuckle on Sun, 23 February 2014 21:34
		Re: Operator precedence By: Richard Damon on Sun, 23 February 2014 23:36
		Re: Operator precedence By: Jerry Stuckle on Mon, 24 February 2014 02:09
		Re: Operator precedence By: Ben Bacarisse on Mon, 24 February 2014 04:49
		Re: Operator precedence By: Thomas 'PointedEars' on Mon, 24 February 2014 11:56
		Re: Operator precedence By: Christoph Michael Bec on Mon, 24 February 2014 16:38
		Re: Operator precedence By: Ben Bacarisse on Mon, 24 February 2014 21:25
		Re: Operator precedence By: Thomas 'PointedEars' on Mon, 24 February 2014 23:38
		Re: Operator precedence By: Christoph Michael Bec on Tue, 25 February 2014 00:07
		Re: Operator precedence By: Thomas 'PointedEars' on Tue, 25 February 2014 00:37
		Re: Operator precedence By: Christoph Michael Bec on Tue, 25 February 2014 01:12
		Re: Operator precedence By: Thomas 'PointedEars' on Tue, 25 February 2014 02:29
		Re: Operator precedence By: Christoph Michael Bec on Tue, 25 February 2014 18:41
		Re: Operator precedence By: Thomas 'PointedEars' on Tue, 25 February 2014 18:55
		Re: Operator precedence By: Christoph Michael Bec on Tue, 25 February 2014 20:36
		Re: Operator precedence By: Ben Bacarisse on Tue, 25 February 2014 03:08
		Re: Operator precedence By: Thomas 'PointedEars' on Tue, 25 February 2014 03:17
		Re: Operator precedence By: Ben Bacarisse on Tue, 25 February 2014 04:45
		Re: Operator precedence By: GS on Tue, 25 February 2014 21:45
		Re: Operator precedence By: Jerry Stuckle on Mon, 24 February 2014 12:00
		Re: Operator precedence By: Christoph Michael Bec on Mon, 24 February 2014 17:11
		Re: Operator precedence By: Jerry Stuckle on Mon, 24 February 2014 19:27
		Re: Operator precedence By: Christoph Michael Bec on Tue, 25 February 2014 00:25
		Re: Operator precedence By: Jerry Stuckle on Tue, 25 February 2014 01:40
		Re: Operator precedence By: Ben Bacarisse on Mon, 24 February 2014 21:23
		Re: Operator precedence By: Jerry Stuckle on Mon, 24 February 2014 21:45
		Re: Operator precedence By: Ben Bacarisse on Tue, 25 February 2014 04:32
		Re: Operator precedence By: Jerry Stuckle on Tue, 25 February 2014 04:47
		Re: Operator precedence By: Ben Bacarisse on Tue, 25 February 2014 16:56
		Re: Operator precedence By: Jerry Stuckle on Tue, 25 February 2014 18:59
		Re: Operator precedence By: Christoph Michael Bec on Tue, 25 February 2014 19:19
		Re: Operator precedence By: Thomas 'PointedEars' on Tue, 25 February 2014 19:43
		Re: Operator precedence By: Jerry Stuckle on Tue, 25 February 2014 21:02
		Re: Operator precedence By: Jerry Stuckle on Tue, 25 February 2014 21:01
		Object constructors/destructors (was: Operator precedence) By: Christoph Michael Bec on Tue, 25 February 2014 21:19
		Re: Object constructors/destructors By: Jerry Stuckle on Tue, 25 February 2014 21:32
		Re: Object constructors/destructors By: Christoph Michael Bec on Tue, 25 February 2014 21:55
		Re: Object constructors/destructors By: Jerry Stuckle on Tue, 25 February 2014 22:01
		Re: Object constructors/destructors By: Adam Harvey on Tue, 25 February 2014 23:22
		Re: Object constructors/destructors By: Jerry Stuckle on Wed, 26 February 2014 02:10
		Re: Object constructors/destructors By: Christoph Michael Bec on Wed, 26 February 2014 20:10
		Re: Object constructors/destructors By: Jerry Stuckle on Wed, 26 February 2014 21:01
		Re: Object constructors/destructors By: Christoph Michael Bec on Wed, 26 February 2014 21:59
		Re: Object constructors/destructors By: Jerry Stuckle on Wed, 26 February 2014 22:19
		Re: Object constructors/destructors By: Christoph Michael Bec on Wed, 26 February 2014 22:39
		Re: Object constructors/destructors By: Jerry Stuckle on Thu, 27 February 2014 03:30
		Re: Object constructors/destructors By: Christoph Michael Bec on Thu, 27 February 2014 17:28
		Re: Object constructors/destructors By: Jerry Stuckle on Thu, 27 February 2014 21:09
		Re: Object constructors/destructors By: Christoph Michael Bec on Fri, 28 February 2014 13:52
		Re: Object constructors/destructors By: Jerry Stuckle on Fri, 28 February 2014 14:08
		Re: Object constructors/destructors By: Christoph Michael Bec on Fri, 28 February 2014 15:52
		Re: Object constructors/destructors By: Jerry Stuckle on Fri, 28 February 2014 16:03
		Re: Object constructors/destructors By: Thomas 'PointedEars' on Thu, 27 February 2014 00:00
		Re: Object constructors/destructors By: Jerry Stuckle on Thu, 27 February 2014 03:39
		Re: Object constructors/destructors By: Thomas 'PointedEars' on Thu, 27 February 2014 17:29
		Re: Object constructors/destructors By: Jerry Stuckle on Thu, 27 February 2014 21:14
		Re: Object constructors/destructors By: Christoph Michael Bec on Tue, 25 February 2014 23:18
		Re: Object constructors/destructors By: Jerry Stuckle on Wed, 26 February 2014 02:08
		Re: Object constructors/destructors By: Richard Damon on Wed, 26 February 2014 12:50
		Re: Object constructors/destructors By: Jerry Stuckle on Wed, 26 February 2014 13:44
		Re: Object constructors/destructors By: Richard Damon on Thu, 27 February 2014 04:49
		Re: Object constructors/destructors By: Jerry Stuckle on Thu, 27 February 2014 13:25
		Re: Object constructors/destructors By: Richard Damon on Sat, 01 March 2014 17:56
		Re: Object constructors/destructors By: Jerry Stuckle on Sat, 01 March 2014 19:22
		Re: Object constructors/destructors By: Richard Damon on Sun, 02 March 2014 19:28
		Re: Object constructors/destructors By: Jerry Stuckle on Sun, 02 March 2014 20:42
		Re: Object constructors/destructors By: Richard Damon on Sun, 02 March 2014 22:14
		Re: Object constructors/destructors By: Jerry Stuckle on Sun, 02 March 2014 22:48
		Re: Object constructors/destructors By: Tim Streater on Sun, 02 March 2014 23:05
		Re: Operator precedence By: Ben Bacarisse on Tue, 25 February 2014 21:08
		Re: Operator precedence By: Christoph Michael Bec on Tue, 25 February 2014 21:29
		Re: Operator precedence By: Ben Bacarisse on Tue, 25 February 2014 23:15
		Re: Operator precedence By: Richard Damon on Tue, 25 February 2014 03:41
		Re: Operator precedence By: Jerry Stuckle on Tue, 25 February 2014 04:59
		Re: Operator precedence By: Richard Damon on Sat, 01 March 2014 18:39
		Re: Operator precedence By: Jerry Stuckle on Sat, 01 March 2014 19:29
		Re: Operator precedence By: Richard Damon on Sun, 02 March 2014 20:22
		Re: Operator precedence By: Jerry Stuckle on Sun, 02 March 2014 20:49
		Re: Operator precedence By: Christoph Michael Bec on Tue, 25 February 2014 18:15
		Re: Operator precedence By: Ben Bacarisse on Sun, 23 February 2014 20:56
		Re: Operator precedence By: Christoph Michael Bec on Mon, 24 February 2014 13:28

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