public function addChild($parent, $child)
    {
        if ($parent->name === $child->name) {
            throw new InvalidArgumentException("Cannot add '{$parent->name}' as a child of itself.");
        }

        if ($parent instanceof Permission && $child instanceof Role) {
            throw new InvalidArgumentException('Cannot add a role as a child of a permission.');
        }

        if ($this->detectLoop($parent, $child)) {
            throw new InvalidCallException("Cannot add '{$child->name}' as a child of '{$parent->name}'. A loop has been detected.");
        }

        $this->db->createCommand()
            ->insert($this->itemChildTable, ['parent' => $parent->name, 'child' => $child->name])
            ->execute();

        $this->invalidateCache();

        return true;
    }
public function addChild($parent, $child)
    {
        if ($parent->name === $child->name) {
            throw new InvalidArgumentException("Cannot add '{$parent->name}' as a child of itself.");
        }

        if ($parent instanceof Permission && $child instanceof Role) {
            throw new InvalidArgumentException('Cannot add a role as a child of a permission.');
        }

        if ($this->detectLoop($parent, $child)) {
            throw new InvalidCallException("Cannot add '{$child->name}' as a child of '{$parent->name}'. A loop has been detected.");
        }

        $this->db->createCommand()
            ->insert($this->itemChildTable, ['parent' => $parent->name, 'child' => $child->name])
            ->execute();

        $this->invalidateCache();

        return true;
    }
{@inheritdoc}