php教程

The AppendIterator class

(PHP 5 >= 5.1.0, PHP 7)

简介

这个迭代器能陆续遍历几个迭代器

类摘要

AppendIterator extends IteratorIterator implements OuterIterator {
/* 方法 */
public __construct ( void )
public append ( Iterator $iterator ) : void
public current ( void ) : mixed
public getArrayIterator ( void ) : ArrayIterator
public getInnerIterator ( void ) : Iterator
public getIteratorIndex ( void ) : int
public key ( void ) : scalar
public next ( void ) : void
public rewind ( void ) : void
public valid ( void ) : bool
/* 继承的方法 */
public IteratorIterator::__construct ( Traversable $iterator )
public IteratorIterator::current ( void ) : mixed
public IteratorIterator::getInnerIterator ( void ) : Traversable
public IteratorIterator::key ( void ) : mixed
public IteratorIterator::next ( void ) : void
public IteratorIterator::rewind ( void ) : void
public IteratorIterator::valid ( void ) : bool
}

Table of Contents

User Contributed Notes

frode at ennerd dot com 06-Sep-2018 08:22
In many cases, especially for streaming sources, Generators are way more efficient. I noticed that the AppendIterator buffers the entire "inner iterator".

<?php
/**
 * This appends $next iterator to $iterator.
 */
function append_iterators(...$iterators){
    foreach($iterators as $iterator)
        foreach($iterator as $row)
            yield($row);
}

/**
 * Merge iterator takes one first from each iterator until
 * every iterator is empty.
 */
function merge_iterators(....$its) {
    $numberOfIts = sizeof($its);
    while($numberOfIts > 0) {
        $iterator = array_shift($its);
        yield($iterator->current());
        $iterator->next();
        if($iterator->valid())
            $its[] = $iterator;
        else
            $numberOfIts--;
    }
});
?>
komalbarun at gmail dot com 16-Mar-2017 03:57
Updated code.
 I could not find how to edit a note :/

Preventing segfault if empty generator.
<?php

$append_iterator = new \AppendIterator();

$generator = some_generator();

// Only works if first value in generator is not empty
// useful when yielding arrays
foreach ($generator as $value)
{
    //If first $value not empty, generator is not empty.
    if(!empty($value))
    {
        $append_iterator->append($generator );
        //break out of loop after appending.
        break;
    }
}
komalbarun at gmail dot com 16-Mar-2017 03:52
Updated code.
 I could not find how to edit a note :/

Preventing segfault if empty generator.
<?php

$append_iterator = new \AppendIterator();

$generator = ReportModel::come_generator();

// Only works if first value in generator is not empty
// useful when yielding arrays
foreach ($append_iterator as $value)
{
    //If first $value not empty, generator is not empty.
    if(!empty($value))
    {
        $append_iterator->append($errors);
        //break out of loop after appending.
    break;
    }
}
koambarun at evolution dot com 16-Mar-2017 05:29
$append_iterator = new \AppendIterator();

$generator = ReportModel::come_generator();

foreach ($errors as $value)
{
    //If first $value not empty, generator is not empty.
    if(!empty($value))
    {
        $append_iterator->append($errors);
        //break out of loop after appending.
    break;
    }
}
joshdifabio at gmail dot com 15-Jun-2016 01:56
Note that AppendIterator will segfault when iterating over an empty generator. Do not use AppendIterator in conjunction with generators.

https://3v4l.org/YC68k

https://bugs.php.net/bug.php?id=71436

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