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Re: out of sheer curiosity... [message #177593 is a reply to message #177585] Tue, 10 April 2012 16:16 Go to previous messageGo to previous message
Jerry Stuckle is currently offline  Jerry Stuckle
Messages: 2598
Registered: September 2010
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On 4/10/2012 11:25 AM, Thomas Mlynarczyk wrote:
> Jerry Stuckle schrieb:
>
>> But you are creating an object without state. When the object state is
>> serialized, by definition it is no longer an object because it has no
>> behavior.
>
> class Foo { public $bar = 42; }
> $foo = new Foo;
> Now, $foo has state but no behaviour. According to you, $foo is not an
> object?
>

If you created a constructor for it, the constructor will be called. If
you don't create your own, a dummy constructor is called, which does
nothing except satisfy the requirement a constructor is called.

> Look, we are all aware that a serialized object is just a dead sequence
> of characters representing the state of the object and that it can be
> used -- together with the class definition -- to reconstruct an object
> which, to the script, will appear to be identical to the original one.
> Now if we just concentrate to what's essential for our script, we can
> say that we "store away" the object in that sequence of characters and
> retrieve it back from there. Simplification for convenience's sake.
>

It is not an object once it has been serialized. To use it, you must
create an object with the deserialized data - which means a constructor
must be called according to OO principles.

>>> Now PDO comes in. When getting a query result as object your
>>> constructor is called
>>> *after* the properties are set.
>>
>> And exactly how is that?
>
> Just as he said. Didn't want to believe it. Wrote a test script. It's
> true. When __construct() is called, the data is already set.
>

OK, not a problem. It doesn't say the constructor must be called after
some properties are set. Just the constructor must be called when the
object is being created and before it is first used.

>> Another problem - you should NEVER call the constructor.
>
> But he doesn't! What makes you think he called the constructor?
>

You have to call a parent's constructor when constructing a child.

> [with true OO languages...]
>> you never have to call the parent constructor, either.
>
> I think that's a bad idea. First: there may be no need to call the
> parent constructor (the child constructor may completely replace it).
> Second: When should the parent constructor be called? Before? After? Or
> maybe somewhere within the child constructor? It's much better and more
> flexible when the child has to call the parent constructor explicitly.
>
> Greetings,
> Thomas
>

No, the child constructor NEVER replaces the parent constructor. The
child's constructor is responsible for creating the child object. The
parent's constructor is responsible for creating the parent object.

For instance, the child can never access private members of the parent
(encapsulation - one of the four attributes of OO languages).

And if the child needs to change the parent like that, you probably have
an invalid design. The child should always extend the parent - not
replace it.

--
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
jstucklex(at)attglobal(dot)net
==================

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