使用RecursiveArrayIterator时如何更改数组键和值？

Question

我怀疑我在这里做了些蠢事,但我对SPL的一个简单问题感到困惑:

如何使用RecursiveArrayIterator/RecursiveIteratorIterator修改数组的内容(本例中的值)？

使用以下测试代码,我可以使用getInnerIterator()和offsetSet()更改循环内的值,并在循环中转储已修改的数组.

但是当我离开循环并从迭代器转储数组时,它又回到了原始值.发生了什么？

$aNestedArray = array();
$aNestedArray[101] = range(100, 1000, 100);
$aNestedArray[201] = range(300, 25, -25);
$aNestedArray[301] = range(500, 0, -50);

$cArray = new ArrayObject($aNestedArray);
$cRecursiveIter = new RecursiveIteratorIterator(new RecursiveArrayIterator($cArray), RecursiveIteratorIterator::LEAVES_ONLY);

// Zero any array elements under 200  
while ($cRecursiveIter->valid())
{
    if ($cRecursiveIter->current() < 200)
    {
        $cInnerIter = $cRecursiveIter->getInnerIterator();
        // $cInnerIter is a RecursiveArrayIterator
        $cInnerIter->offsetSet($cInnerIter->key(), 0);
    }

    // This returns the modified array as expected, with elements progressively being zeroed
    print_r($cRecursiveIter->getArrayCopy());

    $cRecursiveIter->next();
}

$aNestedArray = $cRecursiveIter->getArrayCopy();

// But this returns the original array.  Eh??
print_r($aNestedArray);

Answer 1

似乎普通数组中的值不可修改,因为它们不能通过引用传递ArrayIterator(从该类RecursiveArrayIterator继承其offset*()方法,请参阅SPL参考).所以所有调用offsetSet()都在数组的副本上工作.

我猜他们选择避免​​逐个引用调用,因为它在面向对象的环境中没有多大意义(即,当传递实例ArrayObject应该是默认情况时).

还有一些代码来说明这一点:

$a = array();

// Values inside of ArrayObject instances will be changed correctly, values
// inside of plain arrays won't
$a[] = array(new ArrayObject(range(100, 200, 100)),
             new ArrayObject(range(200, 100, -100)),
             range(100, 200, 100));
$a[] = new ArrayObject(range(225, 75, -75));

// The array has to be
//     - converted to an ArrayObject or
//     - returned via $it->getArrayCopy()
// in order for this field to get handled properly
$a[] = 199;

// These values won't be modified in any case
$a[] = range(100, 200, 50);

// Comment this line for testing
$a = new ArrayObject($a);

$it = new RecursiveIteratorIterator(new RecursiveArrayIterator($a));

foreach ($it as $k => $v) {
    // getDepth() returns the current iterator nesting level
    echo $it->getDepth() . ': ' . $it->current();

    if ($v < 200) {
        echo "\ttrue";

        // This line is equal to:
        //     $it->getSubIterator($it->getDepth())->offsetSet($k, 0);
        $it->getInnerIterator()->offsetSet($k, 0);
    }

    echo ($it->current() == 0) ? "\tchanged" : '';
    echo "\n";
}

// In this context, there's no real point in using getArrayCopy() as it only
// copies the topmost nesting level. It should be more obvious to work with $a
// itself
print_r($a);
//print_r($it->getArrayCopy());

Answer 2

您需要getSubIterator在当前深度调用，offsetSet在该深度使用，并对返回树的所有深度执行相同的操作。

这对于对数组或数组中的值进行无限级别的数组合并和替换非常有用。不幸的是，array_walk_recursive在这种情况下不起作用，因为该函数仅访问叶节点..因此下面 $array 中的“replace_this_array”键将永远不会被访问。

例如，要替换深度未知的数组中的所有值，但仅替换那些包含特定键的值，您可以执行以下操作：

$array = [
    'test' => 'value',
    'level_one' => [
        'level_two' => [
            'level_three' => [
                'replace_this_array' => [
                    'special_key' => 'replacement_value',
                    'key_one' => 'testing',
                    'key_two' => 'value',
                    'four' => 'another value'
                ]
            ],
            'ordinary_key' => 'value'
        ]
    ]
];

$arrayIterator = new \RecursiveArrayIterator($array);
$completeIterator = new \RecursiveIteratorIterator($arrayIterator, \RecursiveIteratorIterator::SELF_FIRST);

foreach ($completeIterator as $key => $value) {
    if (is_array($value) && array_key_exists('special_key', $value)) {
        // Here we replace ALL keys with the same value from 'special_key'
        $replaced = array_fill(0, count($value), $value['special_key']);
        $value = array_combine(array_keys($value), $replaced);
        // Add a new key?
        $value['new_key'] = 'new value';

        // Get the current depth and traverse back up the tree, saving the modifications
        $currentDepth = $completeIterator->getDepth();
        for ($subDepth = $currentDepth; $subDepth >= 0; $subDepth--) {
            // Get the current level iterator
            $subIterator = $completeIterator->getSubIterator($subDepth); 
            // If we are on the level we want to change, use the replacements ($value) other wise set the key to the parent iterators value
            $subIterator->offsetSet($subIterator->key(), ($subDepth === $currentDepth ? $value : $completeIterator->getSubIterator(($subDepth+1))->getArrayCopy()));
        }
    }
}
return $completeIterator->getArrayCopy();
// return:
$array = [
    'test' => 'value',
    'level_one' => [
        'level_two' => [
            'level_three' => [
                'replace_this_array' => [
                    'special_key' => 'replacement_value',
                    'key_one' => 'replacement_value',
                    'key_two' => 'replacement_value',
                    'four' => 'replacement_value',
                    'new_key' => 'new value'
                ]
            ],
            'ordinary_key' => 'value'
        ]
    ]
];

Answer 3

看起来 getInnerIterator 创建了子迭代器的副本。

也许有不同的方法？（敬请关注..）

更新：在对它进行了一段时间的黑客攻击并邀请了另外 3 位工程师之后，PHP 看起来并没有为您提供更改 subIterator 值的方法。

您始终可以使用旧的备用电源：

<?php  
// Easy to read, if you don't mind references (and runs 3x slower in my tests) 
foreach($aNestedArray as &$subArray) {
    foreach($subArray as &$val) {
       if ($val < 200) {
            $val = 0;
        }
    }
}
?>

或者

<?php 
// Harder to read, but avoids references and is faster.
$outherKeys = array_keys($aNestedArray);
foreach($outherKeys as $outerKey) {
    $innerKeys = array_keys($aNestedArray[$outerKey]);
    foreach($innerKeys as $innerKey) {
        if ($aNestedArray[$outerKey][$innerKey] < 200) {
            $aNestedArray[$outerKey][$innerKey] = 0;
        }
    }
}
?>