The CachingIterator class

    (PHP 5, PHP 7, PHP 8)

    Introduzione

    This object supports cached iteration over another iterator.

    Sommario della classe

    class CachingIterator extends IteratorIterator implements ArrayAccess, Countable, Stringable {
    /* Costanti */
    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;
    /* Metodi */
    public __construct(Iterator $iterator, int $flags = CachingIterator::CALL_TOSTRING)
    public count(): int
    public current(): mixed
    public getCache(): array
    public getFlags(): int
    public hasNext(): bool
    public key(): scalar
    public next(): void
    public offsetExists(string $key): bool
    public offsetGet(string $key): mixed
    public offsetSet(string $key, mixed $value): void
    public offsetUnset(string $key): void
    public rewind(): void
    public setFlags(int $flags): void
    public __toString(): string
    public valid(): bool
    /* Metodi ereditati */
    public IteratorIterator::current(): mixed
    public IteratorIterator::getInnerIterator(): ?Iterator
    public IteratorIterator::key(): mixed
    public IteratorIterator::next(): void
    public IteratorIterator::rewind(): void
    public IteratorIterator::valid(): bool
    }

    Costanti predefinite

    CachingIterator::CALL_TOSTRING

    Convert every element to string.

    CachingIterator::CATCH_GET_CHILD

    Don't throw exception in accessing children.

    CachingIterator::TOSTRING_USE_KEY

    Use key for conversion to string.

    CachingIterator::TOSTRING_USE_CURRENT

    Use current for conversion to string.

    CachingIterator::TOSTRING_USE_INNER

    Use inner for conversion to string.

    CachingIterator::FULL_CACHE

    Cache all read data.

    Log delle modifiche

    Versione Descrizione
    8.0.0 CachingIterator implements Stringable now.

    Indice dei contenuti

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    User Contributed Notes 4 notes

    up
    10
    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.
    up
    9
    ahmad dot mayahi at gmail dot com
    8 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());
    ?>
    up
    1
    jerome at chaman dot ca
    5 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)
    up
    0
    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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