iterator_apply

(PHP 5 >= 5.1.0, PHP 7, PHP 8)

iterator_apply — Call a function for every element in an iterator

Beschreibung

iterator_apply(Traversable $iterator, callable $callback, ?array $args = null): int

Calls a function for every element in an iterator.

Parameter-Liste

iterator

The iterator object to iterate over.

callback

The callback function to call on every element. This function only receives the given args, so it is nullary by default. If count($args) === 3, for instance, the callback function is ternary.

Hinweis: The function must return true in order to continue iterating over the iterator.

args

An array of arguments; each element of args is passed to the callback callback as separate argument.

Rückgabewerte

Returns the iteration count.

Beispiele

Beispiel #1 iterator_apply() example

<?php
function print_caps(Iterator $iterator) {
    echo strtoupper($iterator->current()) . "\n";
    return TRUE;
}

$it = new ArrayIterator(array("Apples", "Bananas", "Cherries"));
iterator_apply($it, "print_caps", array($it));
?>

Das oben gezeigte Beispiel erzeugt folgende Ausgabe:

APPLES
BANANAS
CHERRIES

Siehe auch

array_walk() - Wendet eine vom Benutzer gelieferte Funktion auf jedes Element eines Arrays an

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User Contributed Notes 2 notes

down

tezcatl at fedoraproject dot org ¶

6 years ago

Each of the arguments required by the function, must be in the array supplied in the third argument to iterator_apply. You can use references too. Example:

<?php

function translate_to(string $target_language, Iterator $words, array $dictionaries) {
    
    $language = ucfirst($target_language);
    $dictionary = $dictionaries[$target_language] ?? 'not found';
    
    if ($dictionary === 'not found') {
        echo "Not found dictionary for {$language}\n";
        return;
    }
    
    echo "English words translated to {$language}\n";
    
    $not_found = [];
    
    iterator_apply($words, function($words, $dictionary, &$not_found){
    
        $english_word = $words->current();
    
        $translated_word = $dictionary[$english_word] ?? '';
    
        if ($translated_word !== '') {
            echo "{$english_word} translates to {$translated_word}\n";
        } else {
            $not_found[] = $english_word;
        }

        return true;
    
    }, array($words, $dictionary, &$not_found));
    
    echo "\nNot found words:\n" . implode("\n", $not_found) . "\n";
}

$dictionaries = [
    'nahuatl' => [
        'one' => 'Ze',
        'two' => 'Ome',
        'three' => 'Yei',
        'four' => 'Nahui',
    ],
];

$iterator = new \ArrayIterator(array('one', 'two', 'three', 'four', 'gasoil'));

translate_to('nahuatl', $iterator, $dictionaries);
?>

English words translated to Nahuatl
one translates to Ze
two translates to Ome
three translates to Yei
four translates to Nahui

Not found words:
gasoil

down

tezcatl at fedoraproject dot org ¶

6 years ago

Be aware of the proper methods to iterate the specific Iterator you are consuming, as the implementation of the method could vary its behaviour.

For example, unlike the ArrayIterator, you can't iterate on a SplDoubleLinkedList with current() without using next() on every iteration (and then, only would iterate if you return true at the end of the callable. It is far easier then with LinkedLists use a while($it->valid()) { $it->current(); $it->next(); }

Let's see:

<?php

$ll = new \SplDoublyLinkedList();

$ll->push('ze');
$ll->push('ome');
$ll->push('yei');
$ll->push('nahui');

$ll->rewind();

$iterations_done = iterator_apply($ll, function(Iterator $it) {

    echo implode("\t=>", [
        $it->key(),
        $it->current(),
        ucfirst($it->current())
    ]),"\n";
    
    return true;

}, array($ll));

echo "Did iterate {$iterations_done} times \n";

$ll->rewind();

$iterations_done = iterator_apply($ll, function(Iterator $it) {

    echo implode("\t=>", [
        $it->key(),
        $it->current(),
        ucfirst($it->current())
    ]),"\n";
    
    $it->next();
    
    return true;

}, array($ll));

echo "Did iterate {$iterations_done} times \n";

$ll->setIteratorMode(SplDoublyLinkedList::IT_MODE_FIFO | SplDoublyLinkedList::IT_MODE_DELETE);

var_dump($ll->count());

foreach($ll as $key => $val) {
    echo "{$key}\t",ucfirst($val),"\n";
}

var_dump($ll->count());
?>

Output:

0    =>ze    =>Ze
0    =>ze    =>Ze
0    =>ze    =>Ze
0    =>ze    =>Ze
Did iterate 4 times 
0    =>ze    =>Ze
1    =>ome    =>Ome
2    =>yei    =>Yei
3    =>nahui    =>Nahui
Did iterate 4 times 
int(4)
0    Ze
0    Ome
0    Yei
0    Nahui
int(0)

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