SplDoublyLinkedList::setIteratorMode

(PHP 5 >= 5.3.0, PHP 7, PHP 8)

SplDoublyLinkedList::setIteratorMode — Sets the mode of iteration

Description

public SplDoublyLinkedList::setIteratorMode(int $mode): int

Parameters

mode

There are two orthogonal sets of modes that can be set:

The direction of the iteration (either one or the other):
- SplDoublyLinkedList::IT_MODE_LIFO (Stack style)
- SplDoublyLinkedList::IT_MODE_FIFO (Queue style)
The behavior of the iterator (either one or the other):
- SplDoublyLinkedList::IT_MODE_DELETE (Elements are deleted by the iterator)
- SplDoublyLinkedList::IT_MODE_KEEP (Elements are traversed by the iterator)

The default mode is: SplDoublyLinkedList::IT_MODE_FIFO | SplDoublyLinkedList::IT_MODE_KEEP

Warning

The direction of iteration can not be changed for SplStack and SplQueue classes, it is always SplDoublyLinkedList::IT_MODE_FIFO. Trying to modify it will result in a RuntimeException being thrown.

Return Values

Returns the different modes and flags that affect the iteration.

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User Contributed Notes 2 notes

down

gregorypatmore at gmail dot com ¶

13 years ago

Despite the seeming unrelated-ness between the FIFO/LIFO and the KEEP/DELETE option pairs, in respect to the behavior of setIteratorMode they are in some way linked.  Meaning, a second call to setIteratorMode will erase any previous settings even if they are from the other pair.  This, coupled with the default settings for the object (SplDoublyLinkedList::IT_MODE_FIFO | SplDoublyLinkedList::IT_MODE_KEEP), means you have to be careful or you can run into trouble



Consider the following example:



<?php

$l = new SPLDoublyLinkedList();

$l->setIteratorMode(SplDoublyLinkedList::IT_MODE_DELETE);

$l->setIteratorMode(SplDoublyLinkedList::IT_MODE_LIFO);



$mode = $l->getIteratorMode();

var_dump("MODE: $mode");

var_dump("MODE CHECKS");

var_dump(($mode & SplDoublyLinkedList::IT_MODE_LIFO) == SplDoublyLinkedList::IT_MODE_LIFO);

var_dump(($mode & SplDoublyLinkedList::IT_MODE_FIFO) == SplDoublyLinkedList::IT_MODE_FIFO);

var_dump(($mode & SplDoublyLinkedList::IT_MODE_DELETE) == SplDoublyLinkedList::IT_MODE_DELETE);

var_dump(($mode & SplDoublyLinkedList::IT_MODE_KEEP) == SplDoublyLinkedList::IT_MODE_KEEP);



$l->push('A');

$l->push('B');

$l->push('C');

$l->push('D');

$l->rewind();



var_dump("Traversing");

var_dump($l->isEmpty());



var_dump($l->count());

var_dump($l->current());

$l->next();



var_dump($l->count());

var_dump($l->current());

$l->next();



var_dump($l->count());

var_dump($l->current());

$l->next();



var_dump($l->count());

var_dump($l->current());

$l->next();



var_dump($l->count());

var_dump($l->isEmpty());



?>



Which outputs the following:

#############################

string(7) "MODE: 2"



string(11) "MODE CHECKS"

bool(true) #LIFO (ok)

bool(true) #FIFO (umm...wait a minute)

bool(false)#DELETE (houston... wtf)

bool(true) #KEEP (ok, where's the camera hidden)



string(10) "Traversing"

bool(false)



int(4)

string(1) "D"



int(4)

string(1) "C"



int(4)

string(1) "B"



int(4)

string(1) "A"



int(4)

bool(false)

#############################



Basically, you should just check the non-zero flags (LIFO(2) and DELETE(1)).  Since it's an either/or situation within the pairs, this should be able to help you figure out the separate mode pieces an instance has been set to.



example:



<?php

$l = new SPLDoublyLinkedList();

$l->setIteratorMode(SplDoublyLinkedList::IT_MODE_FIFO | SplDoublyLinkedList::IT_MODE_DELETE);



$mode = $l->getIteratorMode();



$isLIFO = ($mode & SplDoublyLinkedList::IT_MODE_LIFO) == SplDoublyLinkedList::IT_MODE_LIFO;



$isDELETE = ($mode & SplDoublyLinkedList::IT_MODE_DELETE) == SplDoublyLinkedList::IT_MODE_DELETE;

?>



hope this helps someone.

down

pritiatwork at gmail dot com ¶

13 years ago

Usage of different Iterator Mode

<?php
$doubly=new SplDoublyLinkedList();
$doubly->push(array('name'=>'Naruto'));
$doubly->push(array('name'=>'Sakura'));
$doubly->push(array('name'=>'Neji'));
$doubly->push(array('name'=>'Sasuke'));
var_dump($doubly);
echo '<br/> FIFO Traversing<br/>';
$doubly->setIteratorMode(SplDoublyLinkedList::IT_MODE_FIFO | SplDoublyLinkedList::IT_MODE_KEEP);
$doubly->rewind();
foreach($doubly as $key=>$value)
{
    echo '<br/>Traversed:'.$key.' '.$value['name'];
}
echo '<br/>LIFO Traversing - Keep mode <br/>';
$doubly->setIteratorMode(SplDoublyLinkedList::IT_MODE_LIFO | SplDoublyLinkedList::IT_MODE_KEEP);
$doubly->rewind();
foreach($doubly as $key=>$value)
{
    echo '<br/>Traversed:'.$key.' '.$value['name'];
}

echo '<br/>LIFO Traversing - Delete mode <br/>';
$doubly->setIteratorMode(SplDoublyLinkedList::IT_MODE_LIFO | SplDoublyLinkedList::IT_MODE_DELETE);
$doubly->rewind();

foreach($doubly as $key=>$value)
{
    if($key == 2) break;
    echo '<br/>Traversed:'.$key.' '.$value['name'];
}
var_dump($doubly);
?>

Output:

FIFO Traversing

Traversed:0 Naruto
Traversed:1 Sakura
Traversed:2 Neji
Traversed:3 Sasuke
LIFO Traversing - Keep mode 

Traversed:3 Sasuke
Traversed:2 Neji
Traversed:1 Sakura
Traversed:0 Naruto
LIFO Traversing - Delete mode 

Traversed:3 Sasuke
object(SplDoublyLinkedList)#1 (2) {
  ["flags":"SplDoublyLinkedList":private]=>
  int(3)
  ["dllist":"SplDoublyLinkedList":private]=>
  array(3) {
    [0]=>
    array(1) {
      ["name"]=>
      string(6) "Naruto"
    }
    [1]=>
    array(1) {
      ["name"]=>
      string(6) "Sakura"
    }
    [2]=>
    array(1) {
      ["name"]=>
      string(4) "Neji"
    }
  }
}

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