CachingIterator 类

(PHP 5, PHP 7, PHP 8)

简介

该对象支持在另一迭代器上缓存迭代。

类摘要

class CachingIterator extends IteratorIterator implements ArrayAccess, Countable, Stringable {
/* 常量 */
public const int CALL_TOSTRING;
public const int CATCH_GET_CHILD;
public const int TOSTRING_USE_KEY;
public const int TOSTRING_USE_CURRENT;
public const int TOSTRING_USE_INNER;
public const int FULL_CACHE;
/* 方法 */
public __construct(Iterator $iterator, int $flags = CachingIterator::CALL_TOSTRING)
public count(): int
public current(): mixed
public getCache(): array
public getFlags(): int
public hasNext(): bool
public key(): scalar
public next(): void
public offsetExists(string $key): bool
public offsetGet(string $key): mixed
public offsetSet(string $key, mixed $value): void
public offsetUnset(string $key): void
public rewind(): void
public setFlags(int $flags): void
public __toString(): string
public valid(): bool
/* 继承的方法 */
public IteratorIterator::next(): void
}

预定义常量

CachingIterator::CALL_TOSTRING

每个元素转换为字符串。

CachingIterator::CATCH_GET_CHILD

访问子元素时不要抛出异常。

CachingIterator::TOSTRING_USE_KEY

转换为字符串时使用 key

CachingIterator::TOSTRING_USE_CURRENT

转换为字符串时使用 current

CachingIterator::TOSTRING_USE_INNER

转换为字符串时使用 inner

CachingIterator::FULL_CACHE

缓存所有读取的数据。

更新日志

版本 说明
8.0.0 CachingIterator 现在实现了 Stringable

目录

add a note add a note

User Contributed Notes 4 notes

up
9
ahmad dot mayahi at gmail dot com
6 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());
?>
up
4
ahmad dot mayahi at gmail dot com
2 years 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.
up
0
xedin dot unknown at gmail dot com
2 years 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.
up
0
jerome at chaman dot ca
2 years 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)
To Top