本文实例讲述了PHP预定义接口——Iterator用法。分享给大家供大家参考,具体如下:
可在内部迭代自己的外部迭代器或类的接口。
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";
}
输出结果:
string ‘myIterator::rewind’ (length=18) string ‘myIterator::valid’ (length=17) string ‘myIterator::current’ (length=19) string ‘myIterator::key’ (length=15) int 0 string ‘first_element’ (length=13) string ‘myIterator::next’ (length=16) string ‘myIterator::valid’ (length=17) string ‘myIterator::current’ (length=19) string ‘myIterator::key’ (length=15) int 1 string ‘second_element’ (length=14) string ‘myIterator::next’ (length=16) string ‘myIterator::valid’ (length=17) string ‘myIterator::current’ (length=19) string ‘myIterator::key’ (length=15) int 2 string ‘last_element’ (length=12) string ‘myIterator::next’ (length=16) string ‘myIterator::valid’ (length=17)
由结果可知,当类实现了Iterator接口,实现改类实例数据集的时候首先会将数据集的键重置,然后逐步后移,每次都会进行然后返回当前元素以及当前键。
希望本文所述对大家PHP程序设计有所帮助。