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

[Robert Lemke]

Hi Martin,

On Mon, 2004-08-09 at 18:16, Martin T. Kutschker wrote:

> The idea is that in a global var we have an array that has references to 
> all classes that need only one instantiation, eg t3lib_db and t3lib_cs.

> Instead of accessing them via a well known global var (eg t3lib_db) or 
> some pre-load mechanism (eg t3lib_cs) the code would simply call the 
> stattic method of tr3lib_div and will get a reference to the object. The 
> code in t3lib_div will either create a new object or pass the reference 
> of an existing one.

okay, but I think that generally it is not a good idea to put
instantiation information about singletons into some global array and
access these functions like you suggested.

How about this: Every class which can be instantiated as a singleton
(like t3lib_cs) must (or may) provide a method called "getInstance".
Then t3lib_div::makeInstance could look like this (didn't check it, may
be done differently):

function &makeInstance($className)	{
   $realClassName =  t3lib_div::makeInstanceClassName($className);
   if (function_exists ($realClassName.'::getInstance')) {
         // Must be done this way, because call_user_func does not
         // return references:
      $tmpObj = $call_user_func (array ($realClassName, 'getInstance));
      return $tmpObj->getInstance();
   } else {
      new $realClassName;
   }
}

This would be 100% backwards-compatible and future code could take
advantage of the singleton mechanism.

-- 
robert

"They placed me on this earth without a manual. 
 And I dare to say, I’m doing just fine without ;)"