The CachingIterator class

(PHP 5, PHP 7, PHP 8)

Giriş

This object supports cached iteration over another iterator.

Sınıf Sözdizimi

class CachingIterator extends IteratorIterator implements ArrayAccess, Countable, Stringable {

/* Sabitler */

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;

/* Yöntemler */

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

/* Miras alınan yöntemler */

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

}

Öntanımlı Sabitler

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.

Sürüm Bilgisi

Sürüm:	Açıklama
8.0.0	CachingIterator implements Stringable now.

İçindekiler

CachingIterator::__construct — Construct a new CachingIterator object for the iterator
CachingIterator::count — The number of elements in the iterator
CachingIterator::current — Return the current element
CachingIterator::getCache — Retrieve the contents of the cache
CachingIterator::getFlags — Get flags used
CachingIterator::hasNext — Check whether the inner iterator has a valid next element
CachingIterator::key — Return the key for the current element
CachingIterator::next — Move the iterator forward
CachingIterator::offsetExists — The offsetExists purpose
CachingIterator::offsetGet — The offsetGet purpose
CachingIterator::offsetSet — The offsetSet purpose
CachingIterator::offsetUnset — The offsetUnset purpose
CachingIterator::rewind — Rewind the iterator
CachingIterator::setFlags — The setFlags purpose
CachingIterator::__toString — Return the string representation of the current element
CachingIterator::valid — Check whether the current element is valid

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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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