<?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());
?>
(PHP 5, PHP 7, PHP 8)
Cet objet supporte les itérations en cache sur un autre itérateur.
CachingIterator::CALL_TOSTRING
Convertit tous les éléments en chaines.
CachingIterator::CATCH_GET_CHILD
N'envoie aucune exception lors de la tentative d'accéder à un enfant.
CachingIterator::TOSTRING_USE_KEY
Utilise key lors de la conversion en chaine.
CachingIterator::TOSTRING_USE_CURRENT
Utilise current lors de la conversion en chaine.
CachingIterator::TOSTRING_USE_INNER
Utilise inner lors de la conversion en chaine.
CachingIterator::FULL_CACHE
Met en cache toutes les données lues.
Version | Description |
---|---|
8.0.0 | La classe CachingIterator implémente désormais Stringable. |
<?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());
?>
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.
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.
"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)