数组过滤器限制结果数PHP

Question

我有以下方法

public function getNextAvailableHousesToAttack(\DeadStreet\ValueObject\House\Collection $collection, $hordeSize)
{
    $houses = $collection->getHouses();

    $housesThatCanBeAttacked = array_filter($houses, function($house) use (&$hordeSize) {
        if(!isset($house)) {
            return false;
        }
        $house = $this->houseModel->applyMaxAttackCapacity($house, $hordeSize);
        if($this->houseModel->isAttackable($house)) {
            return $house;
        }
        return false;
    });

    return $housesThatCanBeAttacked;

但是，此数组可能很大 。

我想限制$housesThatCanBeAttacked到任何大小$hordeSize设置为，因为我只因为有在部落进攻这一轮的僵尸需要尽可能多的房子。

但是，这个$housesThatCanBeAttacked数组$housesThatCanBeAttacked可能包含100万所房屋，而僵尸部落中只有100所房屋。

有没有办法限制通过回调构建的此数组的大小？

Answer 1

您可以简单地使用循环，并在有足够的房子时停止处理数组。

$houses = $collection->getHouses();
housesThatCanBeAttacked[];
$i = 0;

foreach ($houses as $house) {
    $house = $this->houseModel->applyMaxAttackCapacity($house, $hordeSize);
    if ($this->houseModel->isAttackable($house)) {
        housesThatCanBeAttacked[] = $house;
        if (++$i == $hordeSize) {
            break;
        }
    }
}

Answer 2

我会在回调外添加房屋计数器，并在回调内使用它来跳过所有多余的房屋。 解决方案如下所示：

public function getNextAvailableHousesToAttack(\DeadStreet\ValueObject\House\Collection $collection, $hordeSize)
{
    $houses = $collection->getHouses();
    $counter = $hordeSize;

    $housesThatCanBeAttacked = array_filter($houses, function($house) use (&$hordeSize, &$counter) {
        if($counter == 0 && !isset($house)) {
            return false;
        }
        $house = $this->houseModel->applyMaxAttackCapacity($house, $hordeSize);
        if($this->houseModel->isAttackable($house)) {
            $counter--;
            return $house;
        }
        return false;
    });

    return $housesThatCanBeAttacked;

这样，您的array_filter不会返回更多的$counter值。