Re: [PHP-DEV] Traits and static methods
Hi Sebastian,
This is not really a good example as the getInstance() method alone is
not sufficient for a reusable implementation of the Singleton pattern.
Yes, it was just a pseudo-code and not a true singleton implementation.
A trait for a reusable implementation of the Singleton pattern should
look more like
...
which of course does not work as traits are stateless and
Would it work if instance is saved inside a local static var like:
public static function getInstance() {
static $instance = NULL;
if (is_null($instance)) {
$instance = new self();
}
return $instance;
}
/Simas
Re: [PHP-DEV] Traits and static methods
Hi Simas:
On 22 Nov 2010, at 13:47, Simas Toleikis wrote:
Would it work if instance is saved inside a local static var like:
public static function getInstance() {
static $instance = NULL;
if (is_null($instance)) {
$instance = new self();
}
return $instance;
}
http://svn.php.net/viewvc/php/php-src/trunk/Zend/tests/traits/language013.phpt?revision=300283view=markup
The test case says it works ;)
Best regards
Stefan
--
Stefan Marr
Software Languages Lab
Vrije Universiteit Brussel
Pleinlaan 2 / B-1050 Brussels / Belgium
http://soft.vub.ac.be/~smarr
Phone: +32 2 629 2974
Fax: +32 2 629 3525
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Re: [PHP-DEV] Traits and static methods
Hi Simas: Thanks for sending me the test cases. I checked them in, and surprise surprise: it actually was already completely implemented. I didn't had to touch any code... So the missing bit was being more explicit in the RFC. I added a section and an example based on your Singleton code. Now I also remember what the reference to the static modifier was about. You cannot use it to change it for a standard method. That means, if you have a normal method, you cannot make it static however, you can for instance make a public method private, or add an alias for it. That was what that statement was referring to. http://wiki.php.net/rfc/horizontalreuse Hope that helps Best regards Stefan On 17 Nov 2010, at 08:55, Stefan Marr wrote: Hi Simas: On 17 Nov 2010, at 07:32, Simas Toleikis wrote: Alright then, I am sure someone will find more uses for static methods in Traits like factories/utilities (especially if traits can be made to work with late static binding). I assume this will be implemented in one way or another before or after first 5.4 alphas! :) Send me the tests/phpt-files for it, and I will have a lock at it over the weekend. Best regards Stefan -- Stefan Marr Software Languages Lab Vrije Universiteit Brussel Pleinlaan 2 / B-1050 Brussels / Belgium http://soft.vub.ac.be/~smarr Phone: +32 2 629 2974 Fax: +32 2 629 3525 -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php -- Stefan Marr Software Languages Lab Vrije Universiteit Brussel Pleinlaan 2 / B-1050 Brussels / Belgium http://soft.vub.ac.be/~smarr Phone: +32 2 629 2974 Fax: +32 2 629 3525 -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
[PHP-DEV] Traits and static methods
Hello,
I was just skimming through Traits RFC document on the wiki trying to find a
practical use for them. The first thing that comes to my mind is a Singleton
implementation - this is where I found myself literally copying most of
the code in the past. As far as I know there is no way to implement this
pattern properly in PHP without duplicate code (due to lack of multiple
inheritance/templating).
Unfortunately, the same RFC document mentions this for trait methods:
The static modifier is not supported, because it would change the methods
semantics and references to $this would break.
.. and that pretty much defeats Singleton-Trait implementation. Is there any
particular technical/design reasons why traits can't handle $this inside
static methods just like regular static methods do (with a fatal error)?
p.s. a Singleton-Trait implementation could look like:
trait Singleton {
public static function getInstance() { ... }
}
class Child extends Parent {
use Singleton;
}
Child::getInstance();
Re: [PHP-DEV] Traits and static methods
Hi Simas: On 16 Nov 2010, at 18:46, Simas Toleikis wrote: The first thing that comes to my mind is a Singleton implementation - this is where I found myself literally copying most of the code in the past. As far as I know there is no way to implement this pattern properly in PHP without duplicate code (due to lack of multiple inheritance/templating). Unfortunately, the same RFC document mentions this for trait methods: The static modifier is not supported, because it would change the methods semantics and references to $this would break. .. and that pretty much defeats Singleton-Trait implementation. Is there any particular technical/design reasons why traits can't handle $this inside static methods just like regular static methods do (with a fatal error)? Hm, good question. I don't recall any implementation details. Haven't touched the code for too long. From the top of my head, I don't see why it should not work. If I would have elaborated a bit more what I was thinking when I wrote that comment... Following the motto 'it is just compiler assisted copy and paste' I think it should be implemented. Best regards Stefan -- Stefan Marr Software Languages Lab Vrije Universiteit Brussel Pleinlaan 2 / B-1050 Brussels / Belgium http://soft.vub.ac.be/~smarr Phone: +32 2 629 2974 Fax: +32 2 629 3525 -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP-DEV] Traits and static methods
On Tue, Nov 16, 2010 at 6:46 PM, Simas Toleikis sim...@gmail.com wrote:
Hello,
I was just skimming through Traits RFC document on the wiki trying to find
a
practical use for them. The first thing that comes to my mind is a
Singleton
implementation - this is where I found myself literally copying most of
the code in the past. As far as I know there is no way to implement this
pattern properly in PHP without duplicate code (due to lack of multiple
inheritance/templating).
Unfortunately, the same RFC document mentions this for trait methods:
The static modifier is not supported, because it would change the methods
semantics and references to $this would break.
.. and that pretty much defeats Singleton-Trait implementation. Is there
any
particular technical/design reasons why traits can't handle $this inside
static methods just like regular static methods do (with a fatal error)?
p.s. a Singleton-Trait implementation could look like:
trait Singleton {
public static function getInstance() { ... }
}
class Child extends Parent {
use Singleton;
}
Child::getInstance();
for reusable singleton pattern with php 5.3
http://www.slideshare.net/fabpot/design-patternrevisitedphp53
slide 11 and 12
Tyrael
Re: [PHP-DEV] Traits and static methods
On Tue, Nov 16, 2010 at 3:55 PM, Ferenc Kovacs i...@tyrael.hu wrote: for reusable singleton pattern with php 5.3 http://www.slideshare.net/fabpot/design-patternrevisitedphp53 slide 11 and 12 Tyrael The problem with the solution presented in the slides is that it limits every singleton class to only ever be able to inherit from Singleton, so we can't have a child class that is a singleton while the parent is not. Something that having Traits would solve. Though we'd still have singletons, which is a different problem. -Tom -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP-DEV] Traits and static methods
Hi Stefan, Following the motto 'it is just compiler assisted copy and paste' I think it should be implemented. Alright then, I am sure someone will find more uses for static methods in Traits like factories/utilities (especially if traits can be made to work with late static binding). I assume this will be implemented in one way or another before or after first 5.4 alphas! :) /Simas
Re: [PHP-DEV] Traits and static methods
Hi Ferenc,
for reusable singleton pattern with php 5.3
http://www.slideshare.net/fabpot/design-patternrevisitedphp53
slide 11 and 12
As Tom already pointed out - there is that lock-down of your parent(s) to
singletons with this type of implementation and there are other shortcomings
when used with SPL, for example:
class Test extends ArrayObject { }
Without creating some sort of intermediate ArrayObjectSingleton class you
can't make Test a singleton (and traits would solve that).
/Simas
Re: [PHP-DEV] Traits and static methods
Hi Simas: On 17 Nov 2010, at 07:32, Simas Toleikis wrote: Alright then, I am sure someone will find more uses for static methods in Traits like factories/utilities (especially if traits can be made to work with late static binding). I assume this will be implemented in one way or another before or after first 5.4 alphas! :) Send me the tests/phpt-files for it, and I will have a lock at it over the weekend. Best regards Stefan -- Stefan Marr Software Languages Lab Vrije Universiteit Brussel Pleinlaan 2 / B-1050 Brussels / Belgium http://soft.vub.ac.be/~smarr Phone: +32 2 629 2974 Fax: +32 2 629 3525 -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
