從手冊中查到的解釋是:
Iterator extends Traversable {
/* Methods */
abstract public mixed current ( void )
abstract public scalar key ( void )
abstract public void next ( void )
abstract public void rewind ( void )
abstract public boolean valid ( void )
}
當一個實現了Iterator
介面的物件,被foreach
遍歷時,會自動呼叫這些方法。呼叫的循序是:rewind()
-> valid()
-> current()
-> key()
-> next()
下面來看一下簡單的程式碼:
class myIterator implements Iterator {
private $position = 0;
private $array = array(
"firstelement",
"secondelement",
"lastelement",
);
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 => $value) {
var_dump($key, $value);
echo `---------------------------`."
";
}
以上會輸出:
/Users/thanatos/Web/study/blean.php:15:string `myIterator::rewind` (length=18)
/Users/thanatos/Web/study/blean.php:35:string `myIterator::valid` (length=17)
/Users/thanatos/Web/study/blean.php:20:string `myIterator::current` (length=19)
/Users/thanatos/Web/study/blean.php:25:string `myIterator::key` (length=15)
/Users/thanatos/Web/study/blean.php:43:int 0
/Users/thanatos/Web/study/blean.php:43:string `firstelement` (length=12)
---------------------------
/Users/thanatos/Web/study/blean.php:30:string `myIterator::next` (length=16)
/Users/thanatos/Web/study/blean.php:35:string `myIterator::valid` (length=17)
/Users/thanatos/Web/study/blean.php:20:string `myIterator::current` (length=19)
/Users/thanatos/Web/study/blean.php:25:string `myIterator::key` (length=15)
/Users/thanatos/Web/study/blean.php:43:int 1
/Users/thanatos/Web/study/blean.php:43:string `secondelement` (length=13)
---------------------------
/Users/thanatos/Web/study/blean.php:30:string `myIterator::next` (length=16)
/Users/thanatos/Web/study/blean.php:35:string `myIterator::valid` (length=17)
/Users/thanatos/Web/study/blean.php:20:string `myIterator::current` (length=19)
/Users/thanatos/Web/study/blean.php:25:string `myIterator::key` (length=15)
/Users/thanatos/Web/study/blean.php:43:int 2
/Users/thanatos/Web/study/blean.php:43:string `lastelement` (length=11)
---------------------------
/Users/thanatos/Web/study/blean.php:30:string `myIterator::next` (length=16)
/Users/thanatos/Web/study/blean.php:35:string `myIterator::valid` (length=17)