Bug->Req #63154 [Asn->Fbk]: SplDoublyLinkedList should handle list modifications from outside of the object
Edit report at https://bugs.php.net/bug.php?id=63154&edit=1
ID: 63154
Updated by: levim@php.net
Reported by: maciej dot sz at gmail dot com
Summary: SplDoublyLinkedList should handle list modifications
from outside of the object
-Status: Assigned
+Status: Feedback
-Type: Bug
+Type: Feature/Change Request
Package: SPL related
-Operating System: irrelevant
+Operating System: Irrelevant
-PHP Version: 5.4.7
+PHP Version: *
Assigned To: levim
Block user comment: N
Private report: N
New Comment:
I spent a bit of time figuring out why my work-around doesn't work. The reason is when you
remove an element the remaining keys are renumbered. This means that there is no easy way to get
this to work as expected. If we were to change SplDoublyLinkedList to not reorder the keys (which
would make it behave like the ArrayIterator example) it would be a major BC break. I don't
think we can do it. What are your thoughts?
Previous Comments:
------------------------------------------------------------------------
[2012-12-09 02:21:42] levim@php.net
This is not a bug. However, the expected work-around would be:
<?php
$list = new SplDoublyLinkedList();
$list[] = 0;
$list[] = 1;
$list[] = 2;
$list[] = 3;
for ($list->rewind(); $list->valid(); ) {
if (in_array($list->current(), array(0, 2))) {
$list->offsetUnset($list->key());
} else {
$list->next();
}
}
?>
However, this does not work. I am not entirely sure which function/functions
is/are faulty here.
------------------------------------------------------------------------
[2012-09-24 18:44:49] maciej dot sz at gmail dot com
Description:
------------
When I unset more then one element while iterating through SplDoublyLinkedList object it throws an
OutOfRangeException exception. Im guessing that this is because each time an the offsetUnset()
method is called, the keys of the list are reset. This should not be happening until the loop is
rewind()'ed.
Test script:
---------------
$List = new SplDoublyLinkedList();
$List->push('a');
$List->push('b');
$List->push('c');
$List->push('d');
foreach ( $List as $key => $value ) {
echo "Current element: key = {$key}, value = '{$value}'. ";
if ( in_array($value, ['b', 'd']) ) {
echo "MATCH! performing unset";
unset($List[$key]);
}
echo "\n";
}
Expected result:
----------------
The elements should be removed from the list, and no exception should be thrown. At the very least
it should act as the ArrayObject object: triggers a notice, but gets the job done. But the perfect
solution would be the way ArrayIterator does it - clean, no errors:
$Arr = new ArrayIterator(['a', 'b', 'c', 'd']);
foreach ( $Arr as $key => $value ) {
echo "Current element: key = {$key}, value = '{$value}'. ";
if ( in_array($value, ['b', 'd']) ) {
echo "MATCH! performing unset";
unset($Arr[$key]);
}
echo "\n";
}
var_dump($Arr->getArrayCopy());
Actual result:
--------------
OutOfRangeException
------------------------------------------------------------------------
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