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Subject: Re: [PHP-DEV] RFC: Custom Factories (SPL)
From: mathieu.suen@easyflirt.com (Mathieu Suen)

Alban a écrit :
> Le Thu, 19 Nov 2009 02:24:01 +0000, Jared Williams a écrit :
> 
>>> -----Original Message-----
>>> From: Robert Lemke [mailto:robert@typo3.org] Sent: 18 November 2009
>>> 16:07
>>> To: internals@lists.php.net
>>> Subject: [PHP-DEV] RFC: Custom Factories (SPL)
>>>
>>> Hi folks,
>>>
>>> after discussing the idea with various PHP developers I now felt safe
>>> enough that it's not a completely stupid idea to post an RFC for it.
>>> The idea is to add support the registration of custom factories which
>>> are responsible for instantiating certain classes.
>>>
>>> Here is the first draft of my RFC:
>>> http://wiki.php.net/rfc/customfactories
>>>
>>> I suggest that we first discuss the implications and usefulness of this
>>> feature. In a second step I'd need to find some skilled internals
>>> wizard who can implement it, because not being a C developer myself,
>>> all I can offer is making suggestions and fine coffee.
>>>
>>> Looking forward to hearing your comments! Robert
>>>
>>> --
>>> Robert Lemke
>>> Fluent Code Artisan
>>>
>>>
>> Whilst I am a fan of IoC, I don't think its desirable to add language
>> features just to make legacy code more flexible. Surely the route to
>> take is to refactor the legacy code as and when the extra flexibility is
>> needed.
>>
>> Also seems like a possible whole heap of wtf?! When a seemingly absolute
>> statement $a = new A(); gets mangled behind the scenes.
>>
>> Jared
> 
> I'm totaly agree with you Jared !
> I'm a fan of IoC too.
> 
> A factory can provide an object by creating an instance of a class, the 
> choice of the class depends of some paramters. Those parameters can be 
> provided directly by the programmer but also by a final user.
> PHP can not simply "choose" the class to instanciate by checking class's 
> interfaces.
> 
> What Robert Lemke wants to implement is called a "Service" or a 
> "Container". 
> You register a service and call the service instead of calling a class 
> directly. 
> 
> Let me show it in an example of session registration :
> 
> // you register the service
> Services::register('session', 'sessionStoredInCookie');
> 
> // and call it
> $session = Services::load('session');
> 
> Tomorrow, if you want change the session registration mechanism, for 
> storing them in a database for exemple, you have just to change the 
> registred service and whole application has change its session 
> registration method :
> 
> // you register the service
> Services::register('session', 'sessionStoredInDatabase');
> 
> This is very well treated by Fabien Potencier in this document : http://
> fabien.potencier.org/talk/20/decouple-your-code-for-reusability-php-
> forum-2008?position=41 (some parts are in french)
> 
> Implementing a service or container mechanism could be very simple or 
> very complicated. Fabien Potencier use a very complicated example in the 
> link above.
> 
> Use a service or container mechanism (and its implementation) is a 
> developper choice. this could not be traced by php core.
> 
> A service (or container) can create an instance of class or just return 
> an instance of class which is allready created.
> 
> // you register the service
> Services::register('databaseConnexion', new databaseConnexionFactory
> ('mysql', array('server', 'database', 'user', 'password')));
> 
> // and call it
> $db = Services::load('databaseConnexion');
> 
> How PHP should treat the singleton ? getInstance() is just a convention. 
> Create a service mechanism directly in php implies that php implements 
> singleton model too.
> 

Some language have support for IoC. See newspeak:
http://gbracha.blogspot.com/2009/07/ban-on-imports-continued.html


-- Mathieu Suen