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Re: Object constructors/destructors [message #185135 is a reply to message #185134] Fri, 28 February 2014 14:08 Go to previous messageGo to previous message
Jerry Stuckle is currently offline  Jerry Stuckle
Messages: 2598
Registered: September 2010
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On 2/28/2014 8:52 AM, Christoph Michael Becker wrote:
> Jerry Stuckle wrote:
>
>> On 2/27/2014 12:28 PM, Christoph Michael Becker wrote:
>>> Jerry Stuckle wrote:
>>>
>>>> On 2/26/2014 5:39 PM, Christoph Michael Becker wrote:
>>>> > Jerry Stuckle wrote:
>>>> >
>>>> >> No matter how you look at it, PHP's implementation violates OO
>>>> >> principles and works differently than any other OO language.
>>>> >
>>>> > You have claimed that often enough, but yet you have not brought any
>>>> > proof.
>>>> >
>>>> > E.g. what happens in Java if an object that implements the
>>>> > java.io.Serializable interface is given as argument to
>>>> > java.io.OutputStream.writeObject()? Is the destructor called?
>>>> >
>>>>
>>>> Yes, it is.
>>>
>>> I strongly doubt that. On one hand this would mean you can't use the
>>> object as soon as it has been written to the stream, and on the other
>>> hand there are no *destructors* in Java (finalize() is similar to a
>>> destructor, but it is not guaranteed that it will be called).
>>> Furthermore it depends on the garbage collector, when an object will be
>>> *destroyed*.
>>>
>>>> But when the new object is created, a constructor is
>>>> called. You cannot unserialize an object without a constructor being
>>>> called first.
>>>
>>> I doubt that, too. After all, java.io.ObjectInputStream.readObject()
>>> returns an object, which of course has to be *created* -- but there's no
>>> need to call its *constructor*.
>>>
>>
>> No, because the constructor is called automatically.
>
> Wrong, see below.
>
>>> However, I believe our dissent mainly stems from different use of terms.
>>> I am accustomed to understand constructor/destructor as user defined
>>> functions (which can be defined for custom initialization/finalization
>>> tasks), while this may not be the common definition.
>>>
>>
>> They may be user defined, or they may be defined by the system (as in
>> the absence of a user-defined constructor).
>>
>>> When you're talking about OO principles wrt. to
>>> construction/destruction, you're most likely referring to RAII, which is
>>> not necessarily a general OO principle, and might not be possible to be
>>> cleanly implemented in garbage collected languages generally (consider
>>> cyclic references).
>>>
>>
>> No, I am not referring to RAII. I am referring to basic OO principles.
>>
>>> Anyway, I somewhat consider this discussion as harping on about
>>> principles, and I still don't see that PHP lacks the really important
>>> concepts regarding object (de)serialization and cloning.
>>>
>>
>> Just that it doesn't follow OO principles - which has caused me problems
>> in the past.
>
> To shorten further discussion I have installed the JDK 7u51, and written
> the following classes:
>
> ---- Foo.java ----
> public class Foo implements java.io.Serializable {
> protected int bar;
> public Foo() {
> System.out.println("Constructor of Foo called");
> bar = 0;
> }
> public int getBar() {
> return bar;
> }
> public void setBar(int value) {
> bar = value;
> }
> }
>
> ---- Demo.java ----
> import java.io.*;
>
> public class Demo {
> public static void main(String[] args)
> throws IOException, ClassNotFoundException {
> Foo foo = new Foo();
> foo.setBar(42);
> FileOutputStream fileOut = new FileOutputStream("./ser");
> ObjectOutputStream out = new ObjectOutputStream(fileOut);
> out.writeObject(foo);
> out.close();
> fileOut.close();
> System.out.println("Serialized foo");
> System.out.print("bar = ");
> System.out.println(foo.getBar());
> foo = null;
> FileInputStream fileIn = new FileInputStream("./ser");
> ObjectInputStream in = new ObjectInputStream(fileIn);
> foo = (Foo) in.readObject();
> in.close();
> fileIn.close();
> System.out.println("Unserialized foo");
> System.out.print("bar = ");
> System.out.println(foo.getBar());
> }
> }
>
> To compare that with PHP's behavior, I've written the following script:
>
> ---- demo.php ----
> <?php
>
> class Foo
> {
> protected $bar;
> public function __construct() {
> echo "Constructor of Foo called\n";
> $this->bar = 0;
> }
> public function getBar() {
> return $this->bar;
> }
> public function setBar($value) {
> $this->bar = $value;
> }
> }
>
> $foo = new Foo();
> $foo->setBar(42);
> file_put_contents('./ser', serialize($foo));
> echo "Serialized foo\nbar = ", $foo->getBar(), "\n";
> $foo = null;
> $foo = unserialize(file_get_contents('./ser'));
> echo "Unserialized foo\nbar = ", $foo->getBar(), "\n";
>
> Running the java programm and the PHP script (PHP 5.4.19 cli) produces
> the following output:
>
> Constructor of Foo called
> Serialized foo
> bar = 42
> Unserialized foo
> bar = 42
>
> Any conclusions are left to the reader.
>

Which shows just how little you understand programming.

In either case you have not created a new Foo object before serializing;
you have only serialized into an existing object. So obviously no
constructor is called.

Your stoopidity is amazing.

--
==================
Remove the "x" from my email address
Jerry Stuckle
jstucklex(at)attglobal(dot)net
==================

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