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A classe CachingIterator

Introdução

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Sinopse da classe

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

Índice

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User Contributed Notes 4 notes

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8
ahmad dot mayahi at gmail dot com
4 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
7 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
6 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
11 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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