PHP预定义接口——Iterator用法示例

Iterator extends Traversable {
    / 方法 /
    abstract public current ( void ) : mixed
    abstract public key ( void ) : scalar
    abstract public next ( void ) : void
    abstract public rewind ( void ) : void
    abstract public valid ( void ) : bool
}

<?php
class myIterator implements Iterator
{
  private $position = 0;
  private $array = array(
    'first_element',
    'second_element',
    'last_element',
  );

  /
    重置键的位置
   /
  public function rewind(): void
  {
    var_dump(__METHOD__);
    $this->position = 0;
  }

  /
    返回当前元素
   /
  public function current()
  {
    var_dump(__METHOD__);
    return $this->array[$this->position];
  }

  /
    返回当前元素的键
    @return int
   /
  public function key(): int
  {
    var_dump(__METHOD__);
    return $this->position;
  }

  /
    将键移动到下一位
   /
  public function next(): void
  {
    var_dump(__METHOD__);
    ++$this->position;
  }

  /
    判断键所在位置的元素是否存在
    @return bool
   /
  public function valid(): bool
  {
    var_dump(__METHOD__);
    return isset($this->array[$this->position]);
  }
}

$it = new myIterator;

foreach ($it as $key => $value) {
  var_dump($key, $value);
  echo "\n";
}