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

[Martin T. Kutschker]

Robert Lemke wrote:
> 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.

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).

> 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.

But this way you create every time a temp. object, so it's pointless. 
The point is to avoid object creation.

Masi