The CachingIterator class

(PHP 5)

Introduction

This object supports cached iteration over another iterator.

Class synopsis

CachingIterator extends IteratorIterator implements OuterIterator , ArrayAccess , Countable {
/* Constants */
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 ;
/* Methods */
public __construct ( Iterator $iterator [, string $flags = self::CALL_TOSTRING ] )
public int count ( void )
public void current ( void )
public array getCache ( void )
public void getFlags ( void )
public Iterator getInnerIterator ( void )
public void hasNext ( void )
public scalar key ( void )
public void next ( void )
public void offsetExists ( string $index )
public void offsetGet ( string $index )
public void offsetSet ( string $index , string $newval )
public void offsetUnset ( string $index )
public void rewind ( void )
public void setFlags ( bitmask $flags )
public void __toString ( void )
public void valid ( void )
}

Predefined Constants

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.

Table of Contents

Коментарии

<?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());
?>
2016-10-24 22:54:20
http://php5.kiev.ua/manual/ru/class.cachingiterator.html
"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)
2019-12-15 02:37:56
http://php5.kiev.ua/manual/ru/class.cachingiterator.html
The only difference between CachingIterator and other Iterators such as ArrayIterator is the hasNext() method.

Since the data will be loaded into the memory, the CachingIterator is able to check whether the given iterator has a next element.

Let's demonstrate this by an example:

<?php
$iterator 
= new CachingIterator(new ArrayIterator(['C''C++''C#''PHP''Python''Go''Ruby']));

foreach (
$iterator as $item) {
    if (
$iterator->hasNext()) {
        echo 
$item.', ';
    } else {
        echo 
'and '.$item;
    }
}

// C, C++, C#, PHP, Python, Go, and Ruby
?>

In this example I check whether the iterator has a next value, if so, I append a comma otherwise "and" will be appended to the last element.
2020-04-26 00:53:22
http://php5.kiev.ua/manual/ru/class.cachingiterator.html
Apparently, the `FULL_CACHE` flag automatically cancels the default flag `CALL_TOSTRING`. This is evident when one of the values cannot be converted to string: with the default `CALL_TOSTRING` flag, it would throw an error; without that flag, or with the `FULL_CACHE` flag, it does not.
2020-05-07 20:19:39
http://php5.kiev.ua/manual/ru/class.cachingiterator.html

    Поддержать сайт на родительском проекте КГБ