Can Objects be stored in Arrays and still be accessed ?

[Matthias Scheller]

In order to have a form modeled, I would like to store the objects,
which represent the form fields in an array of the object representing
the form.

Nevertheless, the values of the objects in the array can be sometimes
accessed, sometimes not. Any explanations?

Here is a similar code:

<?php
class A {
//for example a form field
var $a;

function set_a($arg){
$this->a=$arg;
}//function
}//class

class B {
//for example a form
var $b=array();
}//class


/*
--here the script Output:

1: 1
2: 2

1:
2:

*/

$ob = new B;
$ob->a[1]=new A;
$ob->a[2]=new A;

foreach($ob->a as $index=>$value) {
$value->set_a($index );
echo $index.': '.$value->a.'<br />' ;
}

foreach($ob->a as $index=>$value) {
echo $index.': '.$value->a.'<br />' ;
}

?>

[Erwin Moller]

Re: Can Objects be stored in Arrays and still be accessed ?

Matthias Scheller wrote:
[color=blue]
> In order to have a form modeled, I would like to store the objects,
> which represent the form fields in an array of the object representing
> the form.
>
> Nevertheless, the values of the objects in the array can be sometimes
> accessed, sometimes not. Any explanations?
>
> Here is a similar code:
>
> <?php
> class A {
> //for example a form field
> var $a;
>
> function set_a($arg){
> $this->a=$arg;
> }//function
> }//class
>
> class B {
> //for example a form
> var $b=array();
> }//class
>
>
> /*
> --here the script Output:
>
> 1: 1
> 2: 2
>
> 1:
> 2:
>
> */
>
> $ob = new B;
> $ob->a[1]=new A;[/color]

???
Where does $ob->a[1] point to?

this is your classdefinition :

class B {
//for example a form
var $b=array();
}//class


Regards,
Erwin

[color=blue]
> $ob->a[2]=new A;
>
> foreach($ob->a as $index=>$value) {
> $value->set_a($index );
> echo $index.': '.$value->a.'<br />' ;
> }
>
> foreach($ob->a as $index=>$value) {
> echo $index.': '.$value->a.'<br />' ;
> }
>
> ?>[/color]

[Alvaro G Vicario]

Re: Can Objects be stored in Arrays and still be accessed ?

*** Matthias Scheller wrote/escribió (Thu, 08 Jul 2004 12:21:34 +0200):[color=blue]
> foreach($ob->a as $index=>$value) {
> $value->set_a($index );
> echo $index.': '.$value->a.'<br />' ;
> }[/color]

The problem is the foreach() constructor. You are not modifying the
original object but a copy.


Manual says:

Note:
Also note that foreach operates on a copy of the specified array and not
the array itself. Therefore, the array pointer is not modified as with the
each() construct, and changes to the array element returned are not
reflected in the original array. However, the internal pointer of the
original array is advanced with the processing of the array. Assuming the
foreach loop runs to completion, the array's internal pointer will be at
the end of the array.


--
--
-- Álvaro G. Vicario - Burgos, Spain
--

[CJ Llewellyn]

Re: Can Objects be stored in Arrays and still be accessed ?

"Matthias Scheller" <schellem@stude nt.ethz.ch> wrote in message
news:ccj72d$p5f $1@newshispeed. ch...[color=blue]
> In order to have a form modeled, I would like to store the objects,
> which represent the form fields in an array of the object representing
> the form.
>
> Nevertheless, the values of the objects in the array can be sometimes
> accessed, sometimes not. Any explanations?[/color]
-snip-[color=blue]
> class B {
> //for example a form
> var $b=array();
> }//class[/color]
-snip-[color=blue]
> $ob = new B;
> $ob->a[1]=new A;
> $ob->a[2]=new A;[/color]

class b doesn't have a member called a.

[Matthias Scheller]

Re: Can Objects be stored in Arrays and still be accessed ?

Matthias Scheller schrieb:
[color=blue]
> In order to have a form modeled, I would like to store the objects,
> which represent the form fields in an array of the object representing
> the form.
>
> Nevertheless, the values of the objects in the array can be sometimes
> accessed, sometimes not. Any explanations?[/color]


Thanks to you all!

The point really was the foreach()-construct, which works on a copy of
the array!
The array was also declared as var $b=array() and adressed as $ob->a,
which helped confusing...

Below, anybody interested will find code to demonstrate the differennt
effect of a for-loop and the foreach-construct:


<?php
class A {
//for example a form field
var $a;

function set_a($arg){
$this->a=$arg;
}//function
}//class

class B {
//for example a form
var $b=array();
}//class


/*
--here the script Output:

1: 1
2: 2

1:
2:

*/

$ob = new B;
$ob->b[0]=new A;
$ob->b[1]=new A;

$size=sizeof($o b->b);
echo $size.'<br />' ;


foreach($ob->b as $index=>$value) {
$value->set_a($index );
echo $index.': '.$value->a.'<br />' ;
}

foreach($ob->b as $index=>$value) {
echo $index.': '.$value->a.'<br />' ;
}


for ($i=0;$i<$size; $i++){
$ob->b[$i]->set_a($i);
echo $i.': '.$ob->b[$i]->a.'<br />' ;
}

for ($i=0;$i<$size; $i++){
echo $i.': '.$ob->b[$i]->a.'<br />' ;
}


?>

[bruno modulix]

Re: Can Objects be stored in Arrays and still be accessed ?

Matthias Scheller a écrit :[color=blue]
> Matthias Scheller schrieb:
>[color=green]
>> In order to have a form modeled, I would like to store the objects,
>> which represent the form fields in an array of the object representing
>> the form.
>>
>> Nevertheless, the values of the objects in the array can be sometimes
>> accessed, sometimes not. Any explanations?[/color]
>
>
>
> Thanks to you all!
>
> The point really was the foreach()-construct, which works on a copy of
> the array![/color]

Note that you can still alter the array :

$a = Array(9, 8, 7, 6)
foreach ($a as $index=>$value) {
$a[$index] = $value + 10;
}

Bruno

[Chung Leong]

Re: Can Objects be stored in Arrays and still be accessed ?

"Matthias Scheller" <schellem@stude nt.ethz.ch> wrote in message
news:ccjhtd$2iq $1@newshispeed. ch...[color=blue]
> Matthias Scheller schrieb:
>[color=green]
> > In order to have a form modeled, I would like to store the objects,
> > which represent the form fields in an array of the object representing
> > the form.
> >
> > Nevertheless, the values of the objects in the array can be sometimes
> > accessed, sometimes not. Any explanations?[/color]
>
>
> Thanks to you all!
>
> The point really was the foreach()-construct, which works on a copy of
> the array!
> The array was also declared as var $b=array() and adressed as $ob->a,
> which helped confusing...[/color]

The most efficient (and less confusing) way to operate on an array is to use
array_walk().

[Jeffrey Silverman]

Re: Can Objects be stored in Arrays and still be accessed ?

yes
--
Jeffrey Silverman
jeffrey@pantsjh u.edu
Drop "pants" to reply by email