如何在使用递归数组生成器时更改数组键和值？

php iterator spl arrayiterator

2022-08-31 01:08:53

我怀疑我在这里做了一些愚蠢的事情，但我对SPL似乎很简单的问题感到困惑：

如何使用递归数组/递归迭代器修改数组的内容（此示例中的值）？

使用下面的测试代码，我可以使用getInnerIterator（）和offsetSet（）更改循环中的值，并在循环中转储修改后的数组。

但是当我离开循环并从迭代器转储数组时，它会返回到原始值。发生了什么事情？

$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);

答案 1

普通数组中的值似乎不可修改，因为它们不能通过引用（从此类继承其方法，请参阅 SPL 引用）的构造函数进行传递。因此，所有调用都对数组的副本进行处理。ArrayIteratorRecursiveArrayIteratoroffset*()offsetSet()

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

一些更多的代码来说明这一点：

$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());

答案 2

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

这对于对数组或数组中的值执行无限级别的数组合并和替换非常有用。不幸的是，在这种情况下将不起作用，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。array_walk_recursive

例如，要替换数组未知级别深处的所有值，但仅替换包含特定键的值，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'
        ]
    ]
];