看看PHP迭代器的内部执行过程
欢迎进入Linux社区论坛,与200万技术人员互动交流 >>进入 下面我们来了解如何实现一个自定义的迭代器,然后再开始慢慢理解迭代器的内部工作原理。先来看一个官方的例子: ?php class myIterator implements Iterator { private $position = 0; private $arra
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下面我们来了解如何实现一个自定义的迭代器,然后再开始慢慢理解迭代器的内部工作原理。先来看一个官方的例子:
class myIterator implements Iterator {
private $position = 0;
private $array = array(
"first_element",
"second_element",
"last_element",
);
public function __construct() {
$this->position = 0;
}
function rewind() {
var_dump(__METHOD__);
$this->position = 0;
}
function current() {
var_dump(__METHOD__);
return $this->array[$this->position];
}
function key() {
var_dump(__METHOD__);
return $this->position;
}
function next() {
var_dump(__METHOD__);
++$this->position;
}
function valid() {
var_dump(__METHOD__);
return isset($this->array[$this->position]);
}
}
$it = new myIterator;
foreach($it as $key => $value) {
echo '输出键值:';
var_dump($key, $value);
//echo $key;
echo "\n";
}
程序运行输出:
string(18) "myIterator::rewind"
string(17) "myIterator::valid"
string(19) "myIterator::current"
string(15) "myIterator::key"
输出键值:int(0)
string(13) "first_element"
string(16) "myIterator::next"
string(17) "myIterator::valid"
string(19) "myIterator::current"
string(15) "myIterator::key"
输出键值:int(1)
string(14) "second_element"
string(16) "myIterator::next"
string(17) "myIterator::valid"
string(19) "myIterator::current"
string(15) "myIterator::key"
输出键值:int(2)
string(12) "last_element"
string(16) "myIterator::next"
string(17) "myIterator::valid"
一般的迭代器内部需要下面的方法:
Iterator::current - Return the current element 返回当前元素
Iterator::key - Return the key of the current element 返回当前元素的键
Iterator::next - Move forward to next element 移向下一个元素
Iterator::rewind - Rewind the Iterator to the first element 重新回到第一个元素
Iterator::valid - Checks if current position is valid 检查当前位置的有效性
如果不是很清楚迭代器的内容工作流程,可以查看下面的迭代器对数组的遍历过程:
/**
* @author nicesunboy@gmail.com
*/
class MyIterator implements Iterator
{
private $var = array();
public function __construct($array)
{
if (is_array($array)) {
$this->var = $array;
}
}
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