PHP デザインパターン(Iteratorパターン)

Iteratorパターン

↓買ったので、JavaをPHPに読み替えて勉強。そのためのメモ。

CD(Cdクラス)をCD棚(CdShelfクラス)に入れて、イテレータで取り出してCDの名前を表示する

<?php
class Cd{
private $name;
public function __construct($name){
$this->name = $name;
}
public function getName(){
return $this->name;
}
}
interface Aggregate{
function iterator();
}
interface myIterator{
function hasNext();
function next();
}
class CdShelf implements Aggregate{
private $Cds;
private $last;
function __construct(){
$this->Cds = array();
$this->last = 0;
}
function iterator(){
return new CdShelfIterator($this);
}
function appendCd($Cd){
$this->Cds[$this->last] = $Cd;
$this->last++;
}
function getCd($index){
return $this->Cds[$index];
}
function getLength(){
return $this->last;
}
}
class CdShelfIterator implements myIterator{
private $CdShelf;
private $index;
function __construct($CdShelf){
$this->CdShelf = $CdShelf;
$this->index = 0;
}
function hasNext(){
if($this->index < $this->CdShelf->getLength()){
return true;
}else{
return false;
}
}
function next(){
$Cd = $this->CdShelf->getCd($this->index);
$this->index++;
return $Cd;
}
}
$CdShelf = new CdShelf;
$CdShelf->appendCd(new Cd("ねぇ"));
$CdShelf->appendCd(new Cd("いきものばかりメンバーズBESTセレクション"));
$CdShelf->appendCd(new Cd("THE BEST BANG!!"));
$CdShelf->appendCd(new Cd("Request"));
$CdShelf->appendCd(new Cd("8UPPERS"));
$CdShelfIterator = $CdShelf->iterator();
while($CdShelfIterator->hasNext()){
$Cd = $CdShelfIterator->next();
print $Cd->getName()."<br/>";
}
?>

PHPのIteratorを使って同じことをやってみる

<?php
class Cd{
private $name;
public function __construct($name){
$this->name = $name;
}
public function getName(){
return $this->name;
}
}
interface Aggregate{
function iterator();
}
class CdShelf implements Aggregate{
private $Cds;
private $last;
function __construct(){
$this->Cds = array();
$this->last = 0;
}
function iterator(){
return new CdShelfIterator($this);
}
function appendCd($Cd){
$this->Cds[$this->last] = $Cd;
$this->last++;
}
function getCd($index){
return $this->Cds[$index];
}
function getLength(){
return $this->last;
}
}
class CdShelfIterator implements Iterator{
private $CdShelf;
private $index;
function __construct($CdShelf){
$this->CdShelf = $CdShelf;
$this->index = 0;
}
function current(){
return $this->CdShelf->getCd($this->index);
}
function key(){
return $this->index;
}
function next(){
++$this->index;
}
function rewind(){
$this->index=0;
}
function valid(){
if( $this->index < $this->CdShelf->getLength() ){
return true;
}else{
return false;
}
}
}
$CdShelf = new CdShelf;
$CdShelf->appendCd(new Cd("ねぇ"));
$CdShelf->appendCd(new Cd("いきものばかりメンバーズBESTセレクション"));
$CdShelf->appendCd(new Cd("THE BEST BANG!!"));
$CdShelf->appendCd(new Cd("Request"));
$CdShelf->appendCd(new Cd("8UPPERS"));
$CdShelfIterator = $CdShelf->iterator();
while($CdShelfIterator->valid()){
$Cd = $CdShelfIterator->current();
print $Cd->getName()."<br/>";
$CdShelfIterator->next();
}
?>

Iteratorを使うとうれしいこと

CDの取り出し(whileループ部分)が、CD棚(CdShelfクラス)の実装と切り離せる。

つまり

CD棚の仕組みを変更したとしても正しいIteratorを返せば、CDの取り出し作業は同じやり方でよくなる。