using the "static" keyword to implement the Singleton pattern

[lawrence]

To call I would do something like:

$headline = McSelectJustOne Field::callData store("cbHeadli ne");

Is this the correct use of the static keyword, to implement a
Singleton design?

class McSelectJustOne Field extends McSelect {
/**
* 11-21-03 - getter
* @param - $infoToBeSought , in this case, is the name of the field
whose contents are wanted.
* returns mixed (could be string or integer or whatever was in the
field)
function static callDatastore($ infoToBeSought) {
$this->setQueryObject ("GetJustOneFie ld");
$this->setInfoToBeSou ght($infoToBeSo ught);
$this->getInfo();
$row = $this->getRowAsArrayW ithStringIndex( $this->dsResultPointe r);
$field = $row[0];
return $field;
}

}

[Phil Roberts]

With total disregard for any kind of safety measures
lk******@geocit ies.com (lawrence) leapt forth and uttered:

To call I would do something like:

$headline = McSelectJustOne Field::callData store("cbHeadli ne");

Is this the correct use of the static keyword, to implement a
Singleton design?

Pretty much, regardless of whether you're using the Singleton
pattern, you're still calling a static method. So the 'static'
keyword is perfectly acceptable.

You ARE using PHP5 I assume?

--
There is no signature.....

[Phil Roberts]

With total disregard for any kind of safety measures
lk******@geocit ies.com (lawrence) leapt forth and uttered:

To call I would do something like:

$headline = McSelectJustOne Field::callData store("cbHeadli ne");
Is this the correct use of the static keyword, to implement a
Singleton design?

Actually, ignore my previous follow-up. No this is not correct. In
PHP5 the correct usage is:

<?php
class Foo {
public static function aStaticMethod() {
// ...
}
}

Foo::aStaticMet hod();
?>

But this is only available in PHP5
--
There is no signature.....

[Phil Roberts]

With total disregard for any kind of safety measures
lk******@geocit ies.com (lawrence) leapt forth and uttered:

To call I would do something like:

$headline = McSelectJustOne Field::callData store("cbHeadli ne");

Is this the correct use of the static keyword, to implement a
Singleton design?

P.P.S: (sorry, I'm a dumbass and my server doesn't refresh quick
enough), the variable $this does not exist within static methods.

--
There is no signature.....

[lawrence]

Phil Roberts <ph*****@HOLYfl atnetSHIT.net> wrote in message news:<Xn******* *************** *@206.127.4.22> ...

With total disregard for any kind of safety measures
lk******@geocit ies.com (lawrence) leapt forth and uttered:

To call I would do something like:

$headline = McSelectJustOne Field::callData store("cbHeadli ne");

Is this the correct use of the static keyword, to implement a
Singleton design?

Pretty much, regardless of whether you're using the Singleton
pattern, you're still calling a static method. So the 'static'
keyword is perfectly acceptable.

You ARE using PHP5 I assume?

No, sorry, I'm not using PHP 5. I'm trying to make this work in PHP 4.

[lawrence]

Phil Roberts <ph*****@HOLYfl atnetSHIT.net> wrote in message news:<Xn******* *************** *@206.127.4.22> ...

With total disregard for any kind of safety measures
lk******@geocit ies.com (lawrence) leapt forth and uttered:

To call I would do something like:

$headline = McSelectJustOne Field::callData store("cbHeadli ne");

Is this the correct use of the static keyword, to implement a
Singleton design?

P.P.S: (sorry, I'm a dumbass and my server doesn't refresh quick
enough), the variable $this does not exist within static methods.

Actually, I'm using the static keyword all wrong. I looked up an old
example that I had almost forgotten. Thank god for Google. This is
what someone suggested to me 8 months ago. I didn't understand it at
the time, but now that I look at it, I realize static is being used
here in a clever way, to get around the limitations of PHP 4.

All this data should only reference one single object. Having only one Object (called Singleton Pattern) can be done by a Mediator (Pattern).
A mediator looks basically like this:

class mediator{

function &instance(){

static $instance;
if (!isset($instan ce)){
$instance = new object;
}

return $instance;
}
}

Which should be referenced absolutely everywhere by

$ins =& mediator::insta nce();

You will then have exactly one object always. Also, you can get rid of all global statements with this.

Brilliant.

[Jochen Daum]

Hi !

(...)

Actually, I'm using the static keyword all wrong. I looked up an old
example that I had almost forgotten. Thank god for Google. This is
what someone suggested to me 8 months ago.

wasn't that long ago.

Jochen
--
Jochen Daum - CANS Ltd.
PHP DB Edit Toolkit -- PHP scripts for building
database editing interfaces.
http://sourceforge.net/projects/phpdbedittk/

[Marcus Baker]

Hi...

lawrence wrote:

Is this the correct use of the static keyword, to implement a
Singleton design?

Why do you need a singleton? Singletons are only a short step up from
globals in causing trouble. They are a right royal pain when testing as
one test can influence another. I wrote an article on the PHP Patterns
site (http://www.phppatterns.com/) on how to get around this issue, and
it involves some serious extra work.

Can you do without it or are you just trying it out as a learning exercise?

yours, Marcus
--
Marcus Baker, ma****@lastcraf t.com, no***@appo.demo n.co.uk

[Jochen Buennagel]

Marcus Baker wrote:

Singletons are only a short step up from globals in causing trouble.
Singletons IMHO avoid the major drawbacks of global objects (which is
the motivation for the pattern if I remember right). They initialize
themselves when first used and they can't be deleted or overwritten by
accident.
They are a right royal pain when testing as one test can influence another.

That depends on the design of your classes and your tests. I usually use
a Factory Method in the client object to get the singleton instance. For
testing I swap that Factory Method out against one that returns a mock
of the Singleton. (I use your Partial Mocks for that.)

Having Singletons carry data that changes after initialization to
reflect the state of the application is indeed problematic, because it
leeds to temporal coupling, which is near impossible to test well. I use
Singletons mainly for "stateless" things that don't change after
initialization. A database connection is a prime example.

Jochen

[lawrence]

Marcus Baker <ma****@lastcra ft.com> wrote in message news:<3F******* *******@lastcra ft.com>...

Hi...

lawrence wrote:

Is this the correct use of the static keyword, to implement a
Singleton design?

Why do you need a singleton? Singletons are only a short step up from
globals in causing trouble. They are a right royal pain when testing as
one test can influence another. I wrote an article on the PHP Patterns
site (http://www.phppatterns.com/) on how to get around this issue, and
it involves some serious extra work.

Can you give a more specific link? Your article is no longer on the
front page. I'd like to read it over.