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【PHP】迭代器模式

作者:PHP设计模式 / 发布于2011/11/29/ 829

<div>?<?php
/**
* 转自 《PHP设计模式》 第十一章： 迭代器模式
* 迭代器：迭代器设计模式可帮助构造特定对象， 那些对象能够提供单一标准接口循环或迭代任何类型的可计数数据。
* 处理需要遍历的可计数数据时， 最佳的解决办法是创建一个基于迭代器设计模式的对象。
*
*/
class CD {

public $band = "";
public $title = "";
public $trackList = array();

public function __construct($band, $title) {
$this->band = $band;
$this->title = $title;
}

public function addTrack($track) {
$this->trackList[] = $track;
}
}
<div>class CDSearchByBandIterator implements Iterator {

private $_CDs = array();
private $_valid = FALSE;

public function __construct($bandName) {
$db = mysql_connect("localhost", "root", "root");
mysql_select_db("test");

$sql = "select CD.id, CD.band, CD.title, tracks.tracknum, tracks.title as tracktitle ";
$sql .= "from CD left join tracks on CD.id = tracks.cid ";
$sql .= "where band = '" . mysql_real_escape_string($bandName) . "' ";
$sql .= "order by tracks.tracknum";

$results = mysql_query($sql);</div>
<div>$cdID = 0;
$cd = NULL;

while ($result = mysql_fetch_array($results)) {
if ($result["id"] !== $cdID) {
if ( ! is_null($cd)) {
$this->_CDs[] = $cd;
}

$cdID = $result['id'];
$cd = new CD($result['band'], $result['title']);
}

$cd->addTrack($result['tracktitle']);
}

$this->_CDs[] = $cd;
}

public function next() {
$this->_valid = (next($this->_CDs) === FALSE) ? FALSE : TRUE;
}

public function rewind() {
$this->_valid = (reset($this->_CDs) === FALSE) ? FALSE : TRUE;
}

public function valid() {
return $this->_valid;
}

public function current() {
return current($this->_CDs);
}

public function key() {
return key($this->_CDs);
}
}
<div>$queryItem = "Never Again";</div>
<div>$cds = new CDSearchByBandIterator($queryItem);</div>
<div>print "<h1>Found the Following CDs</h1>";
print "<table border='1'><tr><th>Band</th><th>Ttile</th><th>Num Tracks</th></tr>";
foreach ($cds as $cd) {
print "<tr><td>{$cd->band}</td><td>{$cd->title}</td><td>";
print count($cd->trackList). "</td></tr>";
}
print "</table>";</div>
<div>/* End of Iterator.class.php */
/* Location the file Design/Iterator.class.php */</div>

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