Question

我正在尝试在PHP（nested dataset structure）中实现another description of the structure的面向对象版本。我已经创建了一个节点实现：

class Node
{
    private $parent;
    private $nodes = [];
    private $level = 1;
    private $left = 1;
    private $right = 2;

    /**
     * @return self|null
     */
    public function getParent()
    {
        return $this->parent;
    }

    private function setParent(self $parent = null)
    {
        $this->parent = $parent;
    }

    public function getLevel(): int
    {
        return $this->level;
    }

    private function setLevel(int $level)
    {
        $this->level = $level;
    }

    public function getLeft(): int
    {
        return $this->left;
    }

    private function setLeft(int $left)
    {
        $this->left = $left;
    }

    public function getRight(): int
    {
        return $this->right;
    }

    private function setRight(int $right)
    {
        $this->right = $right;
    }

    /**
     * @return static[]
     */
    public function getNodes(): array
    {
        return $this->nodes;
    }

    public function addNode(Node $new)
    {
        $new->setLevel($this->getLevel() + 1);
        $this->nodes[] = $new;

        // @todo
    }
}

但是我需要在实现上实现帮助 addNode方法，该方法应在当前节点上添加一个新节点并更新整个树，尤其是新添加的节点，父节点，子节点节点等。

为了使一切变得容易，我创建了一个简单的测试用例，该用例将检查是否正确实现了所有内容：

$country = new Node();
$state = new Node();
$city = new Node();
$country->addNode($state);
$state->addNode($city);

assert($country->getLeft() === 1);
assert($country->getRight() === 6);
assert($country->getLevel() === 1);

assert($state->getLeft() === 2);
assert($state->getRight() === 5);
assert($state->getLevel() === 2);

assert($city->getLeft() === 3);
assert($city->getRight() === 4);
assert($city->getLevel() === 3);

Answer 1

您不应该定义父级或对其的引用，因为您可能会陷入引用循环中，这在代码中不是一件坏事，但在设计中却可能最终使您的代码无法理解出问题了。

对于addNode函数，您似乎处在正确的轨道上，

public function addNode(Node $new)
{
    //no need for getters and setters from inside the class
    $new->level = $this->level + 1;
    $this->nodes[] = $new;
    return $this;
}

我不确定您要使用left和right做什么。但是我认为最上层的父级始终位于左侧，最下层的子级始终位于右侧。在那种情况下，我只是将其与水平区分开来。

我也不会使用private而是使用protected，我在这里主要是这样做的，因此我可以一路向上走，而无需使用getter和setter来使代码紧凑，但是无论如何，您都会感觉到：

class Node
{

    /**
     * @var static
     */
    protected $parent;
    /**
     * @var static[] 
     */
    protected $nodes = [];
    /**
     * @var int 
     */
    protected $level = 1;
    /**
     * @var int 
     */
    protected $left = 0;
    /**
     * @var int 
     */
    protected $right = 0;


    public function addNode(Node $new)
    {
        $new->level = $this->level + 1;
        $new->parent = $this;
        $new->left = $new->level - 1;
        if (empty($this->nodes)) {
            $this->right = 1;
        }
        $curr = $this;
        while (null !== $curr->parent) {
            //walking up to the current parent and telling it there is a new level added
            $curr->parent->right++;
            //setting the current level 1 up
            $curr = $curr->parent;
        }

        $this->nodes[] = $new;
        return $this;
    }
}

由于我返回了$this，因此我可以链接所有内容，或者像这样嵌套addNode调用

$country = new Node();
$state = new Node();
$city = new Node();
$country->addNode($state->addNode($city));

Answer 2

休息一天后喝了一杯咖啡，终于设法完成了。这并不像看起来那样容易，因为添加新节点时必须重写整个树：

public function addChild(Node $new): void
{
    $this->nodes[] = $new;
    $new->setParent($this);
    $new->setLevel($this->getLevel() + 1);
    $new->setLeft($this->getLeft() + 1);
    $new->setRight($this->getLeft() + 2);

    $rootNode = $this;
    while (!empty($rootNode->getParent())) {
        $rootNode = $this->getParent();
    }

    $rootNode->setLeft(1);
    $this->updateTree($rootNode);
}

private function updateTree(Node $node): void
{
    $startIndex = $node->getLeft();
    foreach ($node->getChildren() as $child) {
        $child->setLeft(++$startIndex);
        $child->setRight(++$startIndex);

        if (count($child->getChildren())) {
            $this->updateTree($child);
            $startIndex = $this->getLastChild($child)->getRight();
        }
    }

    $node->setRight($this->getLastChild($node)->getRight() + 1);
}

private function getLastChild(Node $node): Node
{
    return $node->getChildren()[count($node->getChildren()) - 1];
}

该课程即将在GitHub上发布。

PHP中的嵌套数据集结构

2 个答案: