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La clase CachingIterator

(PHP 5, PHP 7, PHP 8)

Introducción

Este objeto admite iteraciones almacenadas en caché sobre otros iteradores.

Sinopsis de la Clase

CachingIterator extends IteratorIterator implements OuterIterator , ArrayAccess , Countable {

/* Constantes */

const integer CALL_TOSTRING = 1 ;

const integer CATCH_GET_CHILD = 16 ;

const integer TOSTRING_USE_KEY = 2 ;

const integer TOSTRING_USE_CURRENT = 4 ;

const integer TOSTRING_USE_INNER = 8 ;

const integer FULL_CACHE = 256 ;

/* Métodos */

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

public count(): int

public current(): void

public getCache(): array

public getFlags(): int

public getInnerIterator(): Iterator

public hasNext(): void

public key(): scalar

public next(): void

public offsetExists(mixed $index): void

public offsetGet(string $index): void

public offsetSet(mixed $index, mixed $newval): void

public offsetUnset(string $index): void

public rewind(): void

public setFlags(int $flags): void

public __toString(): void

public valid(): void

}

Constantes predefinidas

CachingIterator::CALL_TOSTRING: Convierte cada elemento a un string.
CachingIterator::CATCH_GET_CHILD: No lanzar una excepción en el acceso a los hijos.
CachingIterator::TOSTRING_USE_KEY: Usa key para la conversión a string.
CachingIterator::TOSTRING_USE_CURRENT: Usa current para la conversión a string.
CachingIterator::TOSTRING_USE_INNER: Usa inner para la conversión a string.
CachingIterator::FULL_CACHE: Almacena en caché todos los datos leídos.

Tabla de contenidos

CachingIterator::__construct — Construir un nuevo objeto CachingIterator para el iterador
CachingIterator::count — El número de elementos en el iterador
CachingIterator::current — Devuelve el elemento actual
CachingIterator::getCache — Recuperar el contenido de la caché
CachingIterator::getFlags — Obtener las banderas utilizadas
CachingIterator::getInnerIterator — Devuelve el iterador interno
CachingIterator::hasNext — Comprueba que el iterador interno tenga un elemento siguiente válido
CachingIterator::key — Devuelve la clave del elemento actual
CachingIterator::next — Desplaza el iterador adelante
CachingIterator::offsetExists — Comprobar existencia de un índice
CachingIterator::offsetGet — El propósito offsetGet
CachingIterator::offsetSet — El propósito offsetSet
CachingIterator::offsetUnset — El propósito offsetUnset
CachingIterator::rewind — Rebobina el iterador
CachingIterator::setFlags — El propósito de setFlags
CachingIterator::__toString — Devolver la representación en formato cadena del elemento actual
CachingIterator::valid — Comprueba que el elemento actual sea válido

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User Contributed Notes 4 notes

down

ahmad dot mayahi at gmail dot com ¶

7 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());
?>

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ahmad dot mayahi at gmail dot com ¶

4 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.

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xedin dot unknown at gmail dot com ¶

4 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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jerome at chaman dot ca ¶

4 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)

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