类组合而不是对象组合？

Question

我想要一个类属性引用另一个类，而不是它的对象，然后使用该属性来调用该类的静态方法。

class Database { 
    private static $log; 

    public static function addLog($LogClass) { 
     self::$log = $LogClass; 
    } 

    public static function log() { 
     self::$log::write(); // seems not possible to write it like this 
    } 
} 

如何我可以做到这一点？

因为我没有理由让它们成为对象，所以我想为它使用类。

Answer 1

既然你貌似只有在一个特定的方法/功能感兴趣（没有更多的合同/接口），你可以在一个方式，它不要紧写代码无论是静态方法还是对象方法（... hm，对象方法...听起来不对，什么是正确的名称...）或简单的函数。

class LogDummy { 
    public static function write($s) { 
    echo 'LogDummy::write: ', $s, "\n"; 
    } 
    public function writeMe($s) { 
    echo 'LogDummy->writeMe: ', $s, "\n"; 
    } 
} 

class Database { 
    private static $log=null; 

    public static function setLog($fnLog) { 
    self::$log = $fnLog; 
    } 

    public static function log($s) { 
    call_user_func_array(self::$log, array($s)); 
    } 
} 

// static method 
Database::setLog(array('LogDummy', 'write')); 
Database::log('foo'); 

// member method 
$l = new LogDummy; 
Database::setLog(array($l, 'writeMe')); 
Database::log('bar'); 

// plain old function 
function dummylog($s) { 
    echo 'dummylog: ', $s, "\n"; 
} 
Database::setLog('dummylog'); 
Database::log('baz'); 

// anonymous function 
Database::setLog(function($s) { 
    echo 'anonymous: ', $s, "\n"; 
}); 
Database::log('ham'); 

打印

LogDummy::write: foo 
LogDummy->writeMe: bar 
dummylog: baz 
anonymous: ham 

Answer 2

使用call_user_func功能：

class Logger { 
    public static function write($string) { 
     echo $string; 
    } 
} 

class Database { 
    private static $log; 

    public static function addLog($LogClass) { 
     self::$log = $LogClass; 
    } 

    public static function log($string) { 
     call_user_func(array(self::$log, 'write'), $string); 
    } 
} 

$db = new Database(); 
$db->addLog('Logger'); 
$db->log('Hello world!');