La interfaz SeekableIterator

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

Introducción

El iterador Seekable.

Sinopsis de la Interfaz

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

Ejemplo #1 Uso básico

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

<?php
class MiSeekableIterator implements SeekableIterator {

private
$posición = 0;

private
$array = array(
"primer elemento",
"segundo elemento",
"tercer elemento",
"cuarto elemento"
);

/* Métodos requeridos para la interfaz SeekableIterator */

public function seek($posición) {
if (!isset(
$this->array[$posición])) {
throw new
OutOfBoundsException("Posición de búsqueda inválida ($posición)");
}

$this->posición = $posición;
}

/* Métodos requeridos para la interfaz Iterador */

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

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

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

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

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

try {

$it = new MiSeekableIterator;
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:

primer elemento
tercer elemento
segundo elemento
Posición de búsqueda inválida (10)

Tabla de contenidos

add a note

User Contributed Notes 6 notes

up
9
svenr at selfhtml dot org
11 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: 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
0
info at ensostudio dot ru
6 months 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
0
Anonymous
9 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)");
}
?>
up
-8
martin at smasty dot net
11 years ago
The reflection approach:

<?php

$reflection
= new ReflectionClass('MySeekableIterator');
if(
$reflection->hasMethod('seek'))
  echo
"This class has method seek().";

?>
up
-16
marcin dot kleczek at gmail dot com
12 years ago
Better method:

<?php
            $class
= 'SeekableIterator';
           
$findingMethod = 'seek'; // have to be lower chars
          
           
$methods = get_class_methods($class);
          
            foreach(
$methods as $pVal )
                if (
$findingMethod == strtolower($pVal) ) {
                    echo
'This class has method seek().';
                    break;
                }

}

?>

Best method: http://php.net/manual/en/function.method-exists.php
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