Registry Pattern Static Variable

Question

I am currently facing an inconvenience concerning accessing static members of a class served by a Registry Pattern function. The ideal code I would like to use is below. It accesses a constant in the base class, that is served via the static method get() of the registry class.

echo "<link rel='shortcut icon' href='" . Registry::get('base')::SHORTCUT_ICON . "'>";

At the moment I can only work the code like this:

$base = Registry::get('base');
echo "<link rel='shortcut icon' href='" . $base::SHORTCUT_ICON . "'>";

I don't know exactly what this feature would be called, however I thought something similar was being introduced in PHP 5.4 - Access array returned by a function in php. And here https://wiki.php.net/rfc/functionarraydereferencing

Question

Is there a neat one-line solution around this problem, or will it have to remain a messy two-liner?

Why don't you create a simple wrapper around the base value to retrieve static properties? — Bart, Apr 04 '14 at 17:37
@Bart Would you be able to show me the line of code you could use to retrieve a constant from a class returned through a static function? PHP doesn't seem to accept two static accessors (::) in one statement or expression... — Patrick Geyer, Apr 04 '14 at 17:40

score 1 · Answer 1 · answered Apr 04 '14 at 17:59

A very simple way to get around the problem is to create a convenience wrapper for retrieving the static members. A wrapper approach works best if you can provide an instance to wrap around. Since you have a class with static members you will need to have a hardcoded dependency on Registry. Unless you can provide an instance off course.

The ideal situation

class RegistryBaseWrapper {
    private $registry;

    public function __construct(Registry $registry) {
        $this->registry = $registry;
    }

    public function getShortcutIcon() {
        $base = $this->registry::get('base');
        return $base::SHORTCUT_ICON;
    }
}

$wrapper = new RegistryBaseWrapper($registry);
echo $wrapper->getShortcutIcon();

Less ideal but it will work as well

class RegistryBaseWrapper {
    public function getShortcutIcon() {
        $base = Registry->get('base');
        return $base::SHORTCUT_ICON;
    }
}

$wrapper = new RegistryBaseWrapper();
echo $wrapper->getShortcutIcon();

P.s. Don't focus too much on creating oneliners with static variables and direct class references. They will create dependencies which will be hard to manage in the future. If you're writing this code for a quick throw-away project then it's OK. If this is a project that needs future work don't.

Thank you very much for the helpful answer. I will get working on a wrapper class :) — Patrick Geyer, Apr 04 '14 at 18:07

DudeOnRock · Accepted Answer · 2014-04-04T17:28:15.470

0

The only thing I can come up with is this:

constant(get_class(Registry::get('base')).':: SHORTCUT_ICON');

Not sure this is a better solution though, since readability suffers immensely.

Something else you might want to do is to create a getClassName() function in your Registry class, which would just return the name of the class. Then you can do

constant(Registry::getClassName('base').':: SHORTCUT_ICON')

which is a little more clear.

edited Apr 04 '14 at 17:28

answered Apr 04 '14 at 17:15

DudeOnRock

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Thanks a lot for the effort, it's definitely a handy trick, but I still don't think it's what I was looking for. Readability does suffer and I was looking for more of a PHP language struct not a hack around it. It looks like something like that doesn't exist yet :( Thanks again! – Patrick Geyer Apr 04 '14 at 17:20

Registry Pattern Static Variable

2 Answers2