我怀疑我在这里做了一些愚蠢的事情,但我对 SPL 的一个看似简单的问题感到困惑:
如何使用 RecursiveArrayIterator 修改数组的内容(本例中的值)/RecursiveIteratorIterator ?
使用以下测试代码,我可以使用 getInnerIterator() 更改循环内的值和 offsetSet() ,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中转储数组时,它又回到了原始值。发生了什么事?
$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);
最佳答案
似乎普通数组中的值是不可修改的,因为它们不能通过引用传递给 ArrayIterator
的构造函数(RecursiveArrayIterator
继承了它的 offset *()
方法,参见 SPL Reference )。所以对 offsetSet()
的所有调用都在数组的副本上工作。
我猜他们选择避免按引用调用是因为它在面向对象的环境中没有多大意义(即当传递 ArrayObject
的实例时,这应该是默认情况)。
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());
关于php - 如何在使用 RecursiveArrayIterator 时更改数组键和值?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/1228575/