A classe CachingIterator

Introdução

...

Sinopse da classe

CachingIterator extends IteratorIterator implements OuterIterator , Traversable , Iterator , ArrayAccess , Countable {

/* Métodos */

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

public count ( ) : int

public current ( ) : mixed

public getCache ( ) : array

public getFlags ( ) : int

public getInnerIterator ( ) : Iterator

hasNext ( ) : bool

public key ( ) : scalar

next ( ) : void

public offsetExists ( mixed $index ) : void

public offsetGet ( string $index ) : void

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

public offsetUnset ( string $index ) : void

rewind ( ) : void

public setFlags ( int $flags ) : void

__toString ( ) : string

valid ( ) : bool

}

Índice

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::getInnerIterator — Returns the inner iterator
CachingIterator::hasNext — Verifica se o iterador interno tem ou não um próximo elemento válido
CachingIterator::key — Return the key for the current element
CachingIterator::next — Avança o iterador
CachingIterator::offsetExists — The offsetExists purpose
CachingIterator::offsetGet — The offsetGet purpose
CachingIterator::offsetSet — The offsetSet purpose
CachingIterator::offsetUnset — The offsetUnset purpose
CachingIterator::rewind — Recomeça o iterador
CachingIterator::setFlags — The setFlags purpose
CachingIterator::__toString — Retorna a representação como string do elemento atual
CachingIterator::valid — Verifica se o elemento atual é válido ou não

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User Contributed Notes 4 notes

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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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