The CachingIterator class

(PHP 5, PHP 7)

简介

This object supports cached iteration over another iterator.

类摘要

CachingIterator extends IteratorIterator implements OuterIterator , ArrayAccess , Countable {

/* 常量 */

const integer CALL_TOSTRING = 1 ;

const integer CATCH_GET_CHILD = 16 ;

const integer TOSTRING_USE_KEY = 2 ;

const integer TOSTRING_USE_CURRENT = 4 ;

const integer TOSTRING_USE_INNER = 8 ;

const integer FULL_CACHE = 256 ;

/* 方法 */

public __construct ( Iterator $iterator [, int $flags = self::CALL_TOSTRING ] )

public count ( void ) : int

public current ( void ) : mixed

public getCache ( void ) : array

public getFlags ( void ) : int

public getInnerIterator ( void ) : Iterator

public hasNext ( void ) : void

public key ( void ) : scalar

public next ( void ) : void

public offsetExists ( mixed $index ) : void

public offsetGet ( string $index ) : void

public offsetSet ( mixed $index , mixed $newval ) : void

public offsetUnset ( string $index ) : void

public rewind ( void ) : void

public setFlags ( int $flags ) : void

public __toString ( void ) : void

public valid ( void ) : void

}

预定义常量

CachingIterator::CALL_TOSTRING: Convert every element to string.
CachingIterator::CATCH_GET_CHILD: Don't throw exception in accessing children.
CachingIterator::TOSTRING_USE_KEY: Use key for conversion to string.
CachingIterator::TOSTRING_USE_CURRENT: Use current for conversion to string.
CachingIterator::TOSTRING_USE_INNER: Use inner for conversion to string.
CachingIterator::FULL_CACHE: Cache all read data.

CachingIterator::__construct — Construct a new CachingIterator object for the iterator
CachingIterator::count — The number of elements in the iterator
CachingIterator::current — Return the current element
CachingIterator::getCache — Retrieve the contents of the cache
CachingIterator::getFlags — Get flags used
CachingIterator::getInnerIterator — Returns the inner iterator
CachingIterator::hasNext — Check whether the inner iterator has a valid next element
CachingIterator::key — Return the key for the current element
CachingIterator::next — Move the iterator forward
CachingIterator::offsetExists — The offsetExists purpose
CachingIterator::offsetGet — The offsetGet purpose
CachingIterator::offsetSet — The offsetSet purpose
CachingIterator::offsetUnset — The offsetUnset purpose
CachingIterator::rewind — Rewind the iterator
CachingIterator::setFlags — The setFlags purpose
CachingIterator::__toString — Return the string representation of the current element
CachingIterator::valid — Check whether the current element is valid

User Contributed Notes

jerome at chaman dot ca 15-Dec-2019 12:37


"cached iteration over another iterator" means this iterator is always one step behind the inner iterator. In other words, the "first" iteration will yield null:



<?php



$cit = new CachingIterator( new ArrayIterator( [ 'a', 'b', 'c']  ) );



echo $cit->current() ); // null

echo $cit->getInnerIterator()->current() ); // "a"



while($cit->hasNext()){

    

    // we start with a "next" since the "first" item is null

     $cit->next();

     echo $cit->current(), '<br>';

   

}

?>



iterating this way gives us an access, ahead, to the future item (aka current item of the inner iterator)

ahmad dot mayahi at gmail dot com 24-Oct-2016 07:54


<?php

//This snippet will print out all the cached elements (foreach) .



$cache  = new CachingIterator(new ArrayIterator(range(1,100)), CachingIterator::FULL_CACHE);



foreach ($cache as $c) {



}



print_r($cache->getCache());

?>

The CachingIterator class

简介

类摘要

预定义常量

Table of Contents

User Contributed Notes