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Subject: Re: [PHP-DEV] static constructor
From: rowan.collins@gmail.com (Rowan Collins)

Sorry, replying to myself to add a couple of thoughts / clarifications:

Rowan Collins wrote on 13/03/2015 11:53:
> Johannes Ott wrote on 13/03/2015 09:53:
>> Why are in your opinion static members are not allowed to hold more
>> complexe datastructures then simple scalars?
>
> Complex data structures, yes (and I see the use of __static in such 
> cases). Architectural logic gluing one class to another (as in your 
> Logger example), no.

I think I've come up with a better distinction: *state* belongs in 
instances, whereas *data* can exist globally. A logger object 
encapsulates state, so a pointer to one is stateful information; storing 
that state statically is what feels wrong.

A singleton in this case says "there is a bunch of stateful information 
here, but everywhere *in the current code* needs the same instance of it".


>> Please give me one valid
>> argument why I should double all of the functions in my code for a
>> static and non-static access beside the argument that I "have to" use a
>> Singleton.
>
> You don't need to double all the calls. In fact, the majority of your 
> code should not even know the Singleton is there, because they should 
> be treating it as though they have an instance. At certain key points 
> in your code (constructors, the top of methods) you add $foo = 
> Foo::getInstance();, then all your calls look like $foo->doBar();
>
> That's the way I do it, anyway - treat getting the instance for a 
> singleton like importing a variable from global scope, which is 
> basically what it's doing. 

In other words, saying "Foo::getInstance()->bar();" is like using 
"$GLOBALS['foo']->bar();" saying "$foo = Foo::getInstance(); 
$foo->bar();" is like saying "global $foo; $foo->bar();"

The act of retrieving the singleton is separate from the act of using it.

Regards,
-- 
Rowan Collins
[IMSoP]