PHP Conference Nagoya 2025

    The SeekableIterator interface

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

    Introducción

    El iterador Seekable.

    Sinopsis de la Interfaz

    interface SeekableIterator extends Iterator {
    /* Métodos */
    public seek(int $offset): void
    /* Métodos heredados */
    public Iterator::current(): mixed
    public Iterator::key(): mixed
    public Iterator::next(): void
    public Iterator::rewind(): void
    public Iterator::valid(): bool
    }

    Ejemplos

    Ejemplo #1 Uso básico

    Este ejemplo muestra cómo crear un SeekableIterator personalizado, buscar una posición y manejar una posición inválida.

    <?php
    class MySeekableIterator implements SeekableIterator {

    private     $position;

    private     $array = array(
    "first element",
    "second element",
    "third element",
    "fourth element"
    );

    /* Métodos requeridos para la interfaz SeekableIterator */

    public function seek($position) {
    if (!isset(    $this->array[$position])) {
    throw new     OutOfBoundsException("invalid seek position ($position)");
    }

    $this->position = $position;
    }

    /* Métodos requeridos para la interfaz Iterador */

    public function rewind() {
    $this->position = 0;
    }

    public function     current() {
    return     $this->array[$this->position];
    }

    public function     key() {
    return     $this->position;
    }

    public function     next() {
    ++    $this->position;
    }

    public function     valid() {
    return isset(    $this->array[$this->position]);
    }
    }

    try {

    $it = new MySeekableIterator;
    echo     $it->current(), "\n";

    $it->seek(2);
    echo     $it->current(), "\n";

    $it->seek(1);
    echo     $it->current(), "\n";

    $it->seek(10);

    } catch (    OutOfBoundsException $e) {
    echo     $e->getMessage();
    }
    ?>

    El resultado del ejemplo sería algo similar a:

    first element
third element
second element
invalid seek position (10)

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    User Contributed Notes 4 notes

    up
    8
    svenr at selfhtml dot org
    13 years ago
    Best method:

    <?php

    if ($object instanceof SeekableIterator) {
    echo     "\$object has method seek()";
    }

    ?>

    Please, make use of checking if a particular interface has been implemented to assure that the object you are dealing with definately has the methods you are about to use.

    This also works as typehinting:

    <?php

    class foo {
    public function     doSomeSeeking(SeekableIterator $seekMe) {
    $seekMe->seek(10); // will work, otherwise Typehint triggers complaints
    }
    }

    ?>
    up
    1
    info at ensostudio dot ru
    2 years ago
    Note: $offset parameter of SeekableIterator::seek() is position in list, not array key.
    <?php
    $iterator     = new ArrayIterator([1 => "apple", 2 => "banana", 3 => "cherry"]);
    echo     $iterator->offsetGet(2); // banana
    $iterator->seek(2);
    echo     $iterator->current(); // cherry
    ?>
    up
    -1
    info at ensostudio dot ru
    4 years ago
    Note: use array_key_exists instead isset!
    <?php
    public function seek($position)
    {
    $position = (int) $position;
    if (!     array_key_exists($position, array_values($this->array))) {
    throw new     OutOfBoundsException('Invalid position to seek: ' . $position);
    }
    $this->position = $position;
    }
    ?>
    up
    -2
    Anonymous
    11 years ago
    The code above is missing a closing parenthesis.

    <?php
    if (!isset($this->array[$position]) {
    throw new     OutOfBoundsException("invalid seek position ($position)");
    }
    ?>

    should be

    <?php
    if (!isset($this->array[$position])) { // close here
    throw new OutOfBoundsException("invalid seek position ($position)");
    }
    ?>
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