Интерфейс SeekableIterator
(PHP 5 >= 5.1.0)
Введение
Итератор Seekable.
Обзор интерфейсов
Пример #1 Простое использование
Этот пример демонстрирует создание пользовательского итератора SeekableIterator, который ищет позицию и обрабатывает недействильную позицию.
<?php
class MySeekableIterator implements SeekableIterator {
private $position = 0;
private $array = array(
"first element",
"second element",
"third element",
"fourth element"
);
public function seek($position) {
$this->position = $position;
if (!$this->valid()) {
throw new OutOfBoundsException("invalid seek position ($position)");
}
}
/* Методы, необходимые для интерфейса Iterator */
public function __construct() {
$this->position = 0;
}
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 $e->getMessage();
}
?>
Результатом выполнения данного примера будет что-то подобное:
first element third element second element invalid seek position (10)
Содержание
- SeekableIterator::seek — Осуществляет перемещение к заданной позиции
Коментарии
Best method:
<?php
if ($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) {
$seekMe->seek(10); // will work, otherwise Typehint triggers complaints
}
}
?>
The code above is missing a closing parenthesis.
<?php
if (!isset($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 ($position)");
}
?>
Note: use array_key_exists instead isset!<?php
public function seek($position)
{
$position = (int) $position;
if (! array_key_exists($position, array_values($this->array))) {
throw new OutOfBoundsException('Invalid position to seek: ' . $position);
}
$this->position = $position;
}
?>
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
?>