[Typo3-dev] singletons instead of pre-loaded objects

[Martin T. Kutschker]

Robert Lemke wrote:
> On Mon, 2004-08-09 at 20:47, Martin T. Kutschker wrote:
> 
>>Why? You need some place to store the object references. As options I 
>>see either a global array, a master object known to be loaded or factory 
>>objects for every singleton (the object has a method with a static var 
>>as storage).
> 
> Because the recommended way for implementing the Singleton pattern is
> not to store instantiation information in a global variable but use a
> static variable within the class itself (at least that's what I remember
> from the GOF book). 

Have this seen in implementations (XOOPS).

> But with you method, how would I access the object so it could be
> created automatically? 

makeInstance determines if the class is a singleton, if yes, it checks 
the global array if we have an object yet. Otherwise we get a new 
object. If you prefer you can store the objects in a static var of 
makeInstance instead of a global.

>>>      // Must be done this way, because call_user_func does not
>>>      // return references:
 >>>   $tmpObj = call_user_func (array ($realClassName, 'getInstance));

Drats!

This works but is ugly:

class singleton	{

	function &getInstance(&$ref)	{
		static $obj = null;

		if (!is_object($obj))	{ $obj = new singleton(); }
                  // pass back in arg. for call_user_func
		$ref->instance =& $obj;

		return $obj;
	}
}

function &makeInstance($className)	{
    $realClassName =  t3lib_div::makeInstanceClassName($className);
    if (is_callable(array($realClassName, 'getInstance')) {
       call_user_func(array($realClassName, 'getInstance'),&$tmpObj);
       return $tmpObj->instance;
    } else {
       new $realClassName;
    }
}

Now it's fashioned after the book. But I see really no advantage to a 
global.

Masi