The CachingIterator class

(PHP 5, PHP 7)

Introducere

This object supports cached iteration over another iterator.

Sinopsisul clasei

CachingIterator extends IteratorIterator implements OuterIterator , ArrayAccess , Countable {
/* Constante */
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 ;
/* Metode */
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
}

Constante predefinite

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.

Cuprins

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User Contributed Notes 4 notes

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8
ahmad dot mayahi at gmail dot com
3 years ago
<?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());
?>
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1
ahmad dot mayahi at gmail dot com
5 months ago
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.
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0
xedin dot unknown at gmail dot com
5 months ago
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.
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0
jerome at chaman dot ca
10 months ago
"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)
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