PHPで使うGoFパターン ひとり Advent Calendar - ステート

<?php
interface IArticleState {
  public function showArticle ( $article ); 
  public function canShow ( $member ); 
  public function isPublished (); 
}

class Article {
  private $_Subject = null;
  private $_Body = null;
  private $_State = null;

  public function __construct ( $id ) {
    $article =  $this->find ( $id );
    $this->_Subject = $article['sbj'];
    $this->_Body    = $article['body'];

    // 生成はもっと工夫すると良いと思います
    if     ( $article['state'] == 1 ) $this->_State = new ArticleStateOpen ();
    elseif ( $article['state'] == 2 ) $this->_State = new ArticleStateClosed ();
    elseif ( $article['state'] == 3 ) $this->_State = new ArticleStateDraft ();
    else                              throw new Exception ( 'そんなステートありません -> { id:' . $id . ',state:' . $article['state'] );
  }

  public function getState () {
    return $this->_State;
  }
  public function getSubject () {
    return $this->_Subject;
  }

  public function getBody () {
    return $this->_Body;
  }

  public function showArticle () {
    return $this->_State->showArticle ( $this );
  }

  public function canShow ( $member ) {
    return $this->_State->canShow ( $member );
  }

  public function isPublished () {
    return $this->_State->isPublished ();
  }

  //DBからデータ取ってくるイメージで
  public function find ( $id ) {
    $data = array (
      'id-1' => array ( 
        'sbj' => 'article1_subject',
        'body' => 'article1_body',
        'state' => 1,
      ),
      'id-2' => array ( 
        'sbj' => 'article2_subject',
        'body' => 'article2_body',
        'state' => 2,
      ),
      'id-3' => array ( 
        'sbj' => 'article3_subject',
        'body' => 'article3_body',
        'state' => 3,
      ),
    );
    $result = $data['id-' . $id];
    if ( !$result ) throw new Exception ( 'そんな記事はありません id:' .  $id );
    return $result;
  }
}

class ArticleStateOpen implements IArticleState {
  public function showArticle ( $article ) {
    return $article->getSubject () . "\n\n".
       $article->getBody () . "\n";
  }
  public function canShow ( $member ) {
    return true;
  }

  public function isPublished () {
    return true;
  }
}
class ArticleStateClosed implements IArticleState {
  public function showArticle ( $article ) {
    return 'この記事は非公開です';
  }

  public function canShow ( $member ) {
    return false;
  }
  public function isPublished () {
    return false;
  }
}

class ArticleStateDraft implements IArticleState {
  public function showArticle ( $article ) {
    return $article->getSubject () . "(下書き中)\n\n".
       $article->getBody () . "\n";
  }

  public function canShow ( $member ) {
    return $member == '本人です';
  }

  public function isPublished () {
    return false;
  }
}
function say ( $s ) { print "$s\n"; }

$opened = new Article ( 1 );
say ( get_class ( $opened->getState() )  == 'ArticleStateOpen' ? 'OK' : 'NG' );
say ( $opened->canShow ( '本人です' ) == true ? 'OK' : 'NG' );
say ( $opened->canShow ( '本人じゃありません' ) == true ? 'OK' : 'NG' );
say ( $opened->isPublished () == true ? 'OK' : 'NG' );
say ( $opened->showArticle () == "article1_subject\n\narticle1_body\n" ? 'OK' : 'NG' );

$closed = new Article ( 2 );
say ( get_class ( $closed->getState() )  == 'ArticleStateClosed' ? 'OK' : 'NG' );
say ( $closed->canShow ( '本人です' ) == false ? 'OK' : 'NG' );
say ( $closed->canShow ( '本人じゃありません' ) == false ? 'OK' : 'NG' );
say ( $closed->isPublished () == false ? 'OK' : 'NG' );
say ( $closed->showArticle () == "この記事は非公開です" ? 'OK' : 'NG' );

$draft = new Article ( 3 );
say ( get_class ( $draft->getState() )  == 'ArticleStateDraft' ? 'OK' : 'NG' );
say ( $draft->canShow ( '本人です' ) == true ? 'OK' : 'NG' );
say ( $draft->canShow ( '本人じゃありません' ) == false ? 'OK' : 'NG' );
say ( $draft->isPublished () == false ? 'OK' : 'NG' );
say ( $draft->showArticle () == "article3_subject(下書き中)\n\narticle3_body\n" ? 'OK' : 'NG' );