La classe CachingIterator

(PHP 5, PHP 7, PHP 8)

Introduction

Cet objet supporte les itérations en cache sur un autre itérateur.

Synopsis de la classe

class CachingIterator extends IteratorIterator implements ArrayAccess, Countable, Stringable {

/* Constantes */

public const int CALL_TOSTRING;

public const int CATCH_GET_CHILD;

public const int TOSTRING_USE_KEY;

public const int TOSTRING_USE_CURRENT;

public const int TOSTRING_USE_INNER;

public const int FULL_CACHE;

/* Méthodes */

public function __construct(Iterator $iterator, int $flags = CachingIterator::CALL_TOSTRING)

public function count(): int

public function current(): mixed

public function getCache(): array

public function getFlags(): int

public function hasNext(): bool

public function key(): scalar

public function next(): void

public function offsetExists(string $key): bool

public function offsetGet(string $key): mixed

public function offsetSet(string $key, mixed $value): void

public function offsetUnset(string $key): void

public function rewind(): void

public function setFlags(int $flags): void

public function __toString(): string

public function valid(): bool

/* Méthodes héritées */

public function IteratorIterator::current(): mixed

public function IteratorIterator::getInnerIterator(): ?Iterator

public function IteratorIterator::key(): mixed

public function IteratorIterator::next(): void

public function IteratorIterator::rewind(): void

public function IteratorIterator::valid(): bool

}

Constantes pré-définies

CachingIterator::CALL_TOSTRING: Convertit tous les éléments en chaînes.
CachingIterator::CATCH_GET_CHILD: Ne lève pas d'exception lors de la tentative d'accéder à un enfant.
CachingIterator::TOSTRING_USE_KEY: Utilise key lors de la conversion en chaîne.
CachingIterator::TOSTRING_USE_CURRENT: Utilise current lors de la conversion en chaîne.
CachingIterator::TOSTRING_USE_INNER: Utilise inner lors de la conversion en chaîne.
CachingIterator::FULL_CACHE: Met en cache toutes les données lues.

Historique

Version	Description
8.0.0	La classe CachingIterator implémente désormais Stringable.

Sommaire

CachingIterator::__construct — Construit un nouvel objet CachingIterator pour l'itérateur
CachingIterator::count — Le nombre d'éléments de l'itérateur
CachingIterator::current — Retourne l'élément courant
CachingIterator::getCache — Lit le contenu du cache
CachingIterator::getFlags — Lit les options utilisées
CachingIterator::hasNext — Vérifie si l'itérateur interne a un élément suivant valide
CachingIterator::key — Retourne l'index de l'élément courant
CachingIterator::next — Déplace l'itérateur à la position suivante
CachingIterator::offsetExists — Vérifie l'existence d'un offset
CachingIterator::offsetGet — L'élément à lire à la position donnée
CachingIterator::offsetSet — Affecte un nouvel élément à la position donnée
CachingIterator::offsetUnset — Détruit un élément à l'offset indiqué
CachingIterator::rewind — Replace l'itérateur au début
CachingIterator::setFlags — Modifie les options du CachingIterator
CachingIterator::__toString — Retourne la représentation de l'élément courant sous forme de chaîne
CachingIterator::valid — Vérifie si l'élément courant est valide

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User Contributed Notes 4 notes

down

ahmad dot mayahi at gmail dot com ¶

6 years ago

The only difference between CachingIterator and other Iterators such as ArrayIterator is the hasNext() method.

Since the data will be loaded into the memory, the CachingIterator is able to check whether the given iterator has a next element.

Let's demonstrate this by an example:

<?php
$iterator = new CachingIterator(new ArrayIterator(['C', 'C++', 'C#', 'PHP', 'Python', 'Go', 'Ruby']));

foreach ($iterator as $item) {
    if ($iterator->hasNext()) {
        echo $item.', ';
    } else {
        echo 'and '.$item;
    }
}

// C, C++, C#, PHP, Python, Go, and Ruby
?>

In this example I check whether the iterator has a next value, if so, I append a comma otherwise "and" will be appended to the last element.

down

ahmad dot mayahi at gmail dot com ¶

9 years ago

<?php
//This snippet will print out all the cached elements (foreach) .

$cache  = new CachingIterator(new ArrayIterator(range(1,100)), CachingIterator::FULL_CACHE);

foreach ($cache as $c) {

}

print_r($cache->getCache());
?>

down

jerome at chaman dot ca ¶

6 years ago

"cached iteration over another iterator" means this iterator is always one step behind the inner iterator. In other words, the "first" iteration will yield null:

<?php

$cit = new CachingIterator( new ArrayIterator( [ 'a', 'b', 'c']  ) );

echo $cit->current() ); // null
echo $cit->getInnerIterator()->current() ); // "a"

while($cit->hasNext()){
    
    // we start with a "next" since the "first" item is null
     $cit->next();
     echo $cit->current(), '<br>';
   
}
?>

iterating this way gives us an access, ahead, to the future item (aka current item of the inner iterator)

down

xedin dot unknown at gmail dot com ¶

6 years ago

Apparently, the `FULL_CACHE` flag automatically cancels the default flag `CALL_TOSTRING`. This is evident when one of the values cannot be converted to string: with the default `CALL_TOSTRING` flag, it would throw an error; without that flag, or with the `FULL_CACHE` flag, it does not.

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