PHP設計模式

Question

我有一個reoccuring的問題，我目前解決像這樣 -

進來的具有平臺腳本變量後，該平臺是從列表，如：XBOX，PS3，PC ，一個MobileApp，手機遊戲等

爲每個不同的平臺，我希望能夠做不同的事情在我的劇本，但在某些情況下，我想代碼在此刻做的非常類似的事情我做這樣的事情：

$platformArray = array(
    'ps3'=>array('displayName'=>'playstation 3','function'=>'funcPS3'), 
    'xbox'=>array('displayName'=>'Xbox','function'=>'funcXbox') 
) 
//similar amongst all platforms code on line below 
echo 'you have a :'.$platformArray[$_POST['platform']]['displayName'].' for playing  games'; 

call_user_func($platformArray[$_POST['platform']['function']); 

function funcPS3(){ 
    echo 'ps3 specific code'; 
} 

function funcXbox(){ 
    echo 'xbox specific code'; 
} 

我想在我的代碼中使用面向對象的方法，我想要t o現在我使用對象作爲數據存儲介質而不是數組，而我有時需要在代碼中提前定義屬性，但是如何使用對象執行上述操作？

Answer 1

我將從一個非常天真的OO版本開始工作，到使用多態行爲並避免全局狀態的「良好」OO代碼。

1.不多態性，具有全局靜態數據

這是非常糟糕的，因爲它實際上只是在程序代碼的包裝對象。它需要一個函數映射來調用每種類型的平臺。

class Platform {  
    private static $platformArray = array(
     'ps3' => array(
      'displayName'=>'playstation 3', 
      'function'=>'funcPS3' 
     ), 
     'xbox' => array(
      'displayName'=>'Xbox', 
      'function'=>'funcXbox' 
     ) 
    ); 

    private $type; 

    public function __construct($type) { 
     if (!array_key_exists($type, self::$platformArray)) { 
      throw new Exception("Invalid Platform type $type"); 
     } 
     $this->type = $type; 
    } 

    public function printCode() { 
     // This was a question embedded within your question, you can use 
     // http://php.net/manual/en/function.call-user-func.php 
     // and pass an instance with a method name.  
     return call_user_func(array($this, self::$platformArray[$this->type])); 
    } 

    private function funcPS3(){ 
     echo 'ps3 specific code'; 
    } 

    private function funcXbox(){ 
     echo 'xbox specific code'; 
    }  
} 

$plat = new Platform($_POST['platform']); 
$plat->printCode(); 

2.多態...但它仍然使用全局數據

By creating a base class可以實現在子類的行爲，對於每一個關心創建單獨的類。這裏最大的問題是子類需要註冊一個全局註冊表。

abstract class Platform { 
    abstract protected function getCode(); 
    public function printCode() { 
     echo $this->getCode(); 
    } 

    private function __construct() {} // so only factory can instantiate it 
    private static $platformArray = array(); 

    public static function create($type) { 
     if (!array_key_exists($type, self::$platformArray)) { 
      throw new Exception("Invalid Platform type $type"); 
     } 
     return new self::$platformArray[$type]; 

    }   

    public static function addPlatform($type, $ctor) { 
     if (!is_subclass_of($ctor, 'Platform')) { 
      throw new Exception("Invalid Constructor for Platform $ctor"); 
     } 
     self::$platformArray[$type] = $ctor; 
    } 
} 

class PlatformXBox extends Platform{ 
    protected function getCode() { 
     return 'xbox specific code'; 
    } 
} 
Platform::addPlatform('xbox', 'PlatformXBox'); 

class PlatformPs3 extends Platform { 
    protected function getCode() { 
     return 'ps3 specific code'; 
    } 
} 
Platform::addPlatform('ps3', 'PlatformPs3'); 

$plat = Platform::create($_POST['platform']); 
$plat->printCode(); 

3.多態，沒有全球性的數據

By putting your code into a namespace，您避免在基類的靜態代碼，避免映射後的參數的危險直接進入類。

namespace platform { 

interface IPlatform { 
    public function getDisplayName(); 
    public function getCode(); 
} 

class PlatformFactory { 
    static public function create($platformType) {   
     $className = "\\platform\\$platformType"; 
     if (!is_subclass_of($className, "\\platform\\IPlatform")){ 
      return null; 
     } 
     return new $className; 
    } 
} 

class Xbox implements IPlatform { 
    public function getDisplayName(){ 
     return 'xbox'; 
    } 
    public function getCode(){ 
     return 'xbox code'; 
    } 
} 

class Ps3 implements IPlatform { 
    public function getDisplayName(){ 
     return 'ps3'; 
    } 
    public function getCode(){ 
     return 'ps3 code'; 
    } 
} 

} 

現在你可以使用這些類像下面

$platform = platform\PlatformFactory::create('xbox'); 
echo $platform->getCode() ."\n" ; 

$platform2 = platform\PlatformFactory::create('ps3'); 
echo $platform2->getDisplayName()."\n"; 

$noPlatform = platform\PlatformFactory::create('dontexist'); 
if ($noPlatform) { 
    echo "This is bad, plaftorm 'dontexist' shouldn't have been created"; 
} else { 
    echo "Platform 'dontexist' doesn't exist"; 
} 

Answer 2

您可能希望創建一個類叫做平臺和類的每個平臺的不同方法中：

class platforms { 
    //Create your variables here, also called properties. 
    public $displayName; 

    //Create a function, also called a method for each platform you intent to use. 
    public function xboxPlatform(){ 
     //Code comes here what you want to do. 
    } 
} 

希望這可以幫助。

Answer 3

我會建議你首先理解多態性。 This lecture應該是個好的開始。

當你試圖創建行爲，基於某些標誌，你應該實現兩個類具有相同的接口：

class Xbox 
{ 
    private $displayName = 'XBox 360'; 

    public function identify() 
    { 
     // Xbox-specific stuff 
     return ':::::::::::'. $this->displayName; 
    } 
} 

class PS3 
{ 

    private $displayName = 'Playstation 3'; 

    public function identify() 
    { 
     // playstation-specific stuff 
     return '+++'. $this->displayName . '+++'; 
    } 
} 

這兩個類有法同名，會做不同的事情;

$platform = $_POST['platform']; 
// classes in PHP are case-insensitive 
// expected values would be: xbox, Xbox, ps3, pS3 
if (!class_exists($platform)) 
{ 
    echo "Platform '{$platform}' is not supported"; 
    exit; 
    // since continuing at this point would cause a fatal error, 
    // better to simply exit 
} 

$object = new $platform; 
echo $object->identify(); 

基本上，在這種情況下，你真的不在乎，你正在使用哪種類型的平臺。所有你需要知道的是它們都有相同的公共接口。這被稱爲「多態行爲」。