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Re: Object constructors/destructors [message #185149 is a reply to message #185147] Sun, 02 March 2014 20:42 Go to previous messageGo to previous message
Jerry Stuckle is currently offline  Jerry Stuckle
Messages: 2598
Registered: September 2010
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On 3/2/2014 2:28 PM, Richard Damon wrote:
> On 3/1/14, 2:22 PM, Jerry Stuckle wrote:
>> On 3/1/2014 12:56 PM, Richard Damon wrote:
>>> On 2/27/14, 8:25 AM, Jerry Stuckle wrote:
>>>> On 2/26/2014 11:49 PM, Richard Damon wrote:
>>>> > On 2/26/14, 8:44 AM, Jerry Stuckle wrote:
>>>> >> On 2/26/2014 7:50 AM, Richard Damon wrote:
>>>> >>>
>>>> >>> An the "name" of the Deserializing constructor in PHP is __wakeup().
>>>> >>>
>>>> >>> You also do NOT get two destructor calls on the same object, the
>>>> >>> deserializing created a new object.
>>>> >>>
>>>> >>
>>>> >> __wakeup() is not a constructor - and does not do the same thing.
>>>> >>
>>>> >
>>>> > What makes it NOT a constructor? IT seems to be exactly the thing that
>>>> > does what you say must be done to make the new object via
>>>> > unserialization.
>>>> >
>>>>
>>>> If you want to consider __wakeup() to be a constructor, then you must
>>>> consider __sleep() to be a destructor. In that case, PHP is also wrong
>>>> because if an object is serialized, it will call both __sleep() and the
>>>> destructor. This would be two calls to destructors for the same object.
>>>>
>>>
>>> WHY does __sleep() need to be a destructor?
>>>
>>> __sleep() is a function to control how an object is serialized, and the
>>> object, as you seem to know, still exists, so no destructor should
>>> happen at this point, in fact, if you look at it, __sleep() has not
>>> expected to have any effect on the current object, its purpose is to
>>> make sure that __wakeup() will get all the data it needs, and allow the
>>> removal of data that it won't need.
>>>
>>
>> If you are going to claim __wakeup() is a constructor, then you have to
>> agree that it's opposite (__sleep()) is a destructor. Otherwise you are
>> being inconsistent.
>>
>> You can't just make up rules as you see fit!
>>
>
> Then why are you claiming that something that isn't a desturctor must be
> one.
>

I'm not - you're the one claiming __wakeup() is a constructor, but it's
opposite, __sleep() is not a destructor.

> Serialization, creates an external representation for an object, that is
> what __sleep() is part of. This does NOT inherently involve the
> destruction of the object (at least at that point).
>

Then __wakeup() does NOT inherently involve creation of an object.

> Deserialization, on the other hand, creates an object from an external
> representation. so it will involve the construction of a new object (you
> can do "in-place" deserialization in some languages, where you first
> create a dummy object, and then fill it in with the external data, but
> this is normally a clumsy way to define it).
>

Not in other languages. It builds from an already existing object where
the constructor has been called.

> Note that the object oriented paradigm does have asymmetry in it. A
> given type will tend to have multiple constructors, for the different
> ways that an object might come into existence. There is usually only one
> destructor. In PHP, one of these constructors is called __construct()
> which is the general purpose constructor. (unlike in other statically
> type languages, we can only define one of these). PHP also lets us
> define a piece of the deserialing constructor with __wakeup() (PHP does
> some of the heavy lifting here in parsing the serialized data and
> setting up the object, __wakeup() is just required to do any final
> needed operations after the values have been set.)
>

Constructors are constructors, and the destructor is a destructor. No
asymmetry there. Except in PHP.


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==================
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Jerry Stuckle
jstucklex(at)attglobal(dot)net
==================
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