Re: Static initialization block support in Class?

On 17.08.2010, at 10:46, Ferenc Kovacs wrote: > Tue, Aug 17, 2010 at 10:04 AM, Richard Quadling <rquadling@gmail.com>wrote: > >> On 17 August 2010 08:39, Jingcheng Zhang <diogin@gmail.com> wrote: >>> Hello internals, >>> >>> I wonder whether it is possible to implement "static initialization >> block" >>> feature in PHP, for example: >>> >>> <?php >>> class Foo { >>> >>> } >>> class Bar { >>> public static $baz = 'baz'; >>> public static $foo; >>> static { >>> // After loading this file, self::$foo is initialized as a Foo >>> instance. >>> self::$foo = new Foo(); >>> } >>> } >>> ?> >>> >>> Currently we have to do this outside the class definition as static >> variable >>> initialization is only limited to constant values. >>> However in some circumstance, "dynamic" initialization of static variable >> is >>> expected and meaningful. >>> >>> Thanks in advance! >>> >>> -- >>> Best regards, >>> Jingcheng Zhang >>> P.R.China >>> >> >> Implementing a singleton method is a common solution and one that is >> well understood and documented. >> >> Another option would be to put the initialisation immediately after >> the class definition, so once the class is loaded, a static instance >> is prepared. This saves the consumer of the class from having to do 1 >> additional line of code. >> >> Or you could load the public static methods with a JIT call to prepare >> the static instance. Overhead is that every call will have to test >> self::$instance >> >> >> There is probably some argument against "statics" being "dynamic" >> though ... not my area of expertise to argue either way. >> >> -- >> Richard Quadling. >> >> -- >> PHP Internals - PHP Runtime Development Mailing List >> To unsubscribe, visit: http://www.php.net/unsub.php >> >> > This was brought up in the past: > > http://www.mail-archive.com/internals@lists.php.net/msg46458.html > I still think that it's weird, that I can define a constant to a dynamic > value (eg. by a complex expression or a function's return value), but I > can't do that with the class consts. and with 5.3, we have two different > kind of consts, you can define constants in compile time with const where > you can't use expressions, and you can use the define method, where you can > use expressions. > and you can combine them: > > define("NOW", time()); > var_dump(NOW); > const BAR = NOW; > var_dump(BAR); > class baz{ > const BAR = NOW; > } > var_dump(baz::BAR);' > > with that in mind, I think we could allow complex expression to the const: > the expression will be stored as-is, and when it's referenced (JIT) then it > will be evaluated. > > and this could be used also for variables also: > > class foo{ > public $now = time(); > } > $foo = new foo; > echo $foo->now; > > ps: I predict somebody will say: can of worms! :) > > Tyrael Can do: can of worms. To the original poster: use a singleton or add the init declarations after the class declaration, works just fine with autoloads (I recommend the singleton approach). - David

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