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The SeekableIterator interface


The SeekableIterator interface

Introduction

The Seekable iterator.

Interface synopsis

SeekableIterator extends Iterator {
/* Methods */
abstract public void seek ( int $position )
/* Inherited methods */
abstract public mixed Iterator::current ( void )
abstract public scalar Iterator::key ( void )
abstract public void Iterator::next ( void )
abstract public void Iterator::rewind ( void )
abstract public boolean Iterator::valid ( void )
}

Example #1 Basic usage

This example demonstrates creating a custom SeekableIterator, seeking to a position and handling an invalid position.

<?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)");
      }
    }

    
/* Methods required for Iterator interface */
    
    
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();
}
?>

The above example will output something similar to:

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

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