A magic memoization function
This package contains a once
function. You can pass a callable
to it. Here's quick example:
$myClass = new class() {
public function getNumber(): int
{
return once(function () {
return rand(1, 10000);
});
}
};
No matter how many times you run $myClass->getNumber()
inside the same request you'll always get the same number.
Under the hood, this package uses a PHP 8 Weakmap. In this video, you'll see what a weakmap is, together with a nice demo of the package.
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You can install the package via composer:
composer require spatie/once
The once
function accepts a callable
.
$myClass = new class() {
public function getNumber(): int
{
return once(function () {
return rand(1, 10000);
});
}
};
No matter how many times you run $myClass->getNumber()
you'll always get the same number.
The once
function will only run once per combination of argument values the containing method receives.
class MyClass
{
/**
* It also works in static context!
*/
public static function getNumberForLetter($letter)
{
return once(function () use ($letter) {
return $letter . rand(1, 10000000);
});
}
}
So calling MyClass::getNumberForLetter('A')
will always return the same result, but calling MyClass::getNumberForLetter('B')
will return something else.
To flush the entire cache you can call:
Spatie\Once\Cache::getInstance()->flush();
In your tests you probably don't want to cache values. To disable the cache you can call:
Spatie\Once\Cache::getInstance()->disable();
You can re-enable the cache with
Spatie\Once\Cache::getInstance()->enable();
Warning
This behaviour is in beta and needs to be tested by the community. You can find this topic in discussion #79.
In order to have once
working properly in an Octane environment, Cache::getInstance()->flush()
must be called when OperationTerminated
event is triggered. You can configure it in config/octane.php
file:
// config/octane.php
OperationTerminated::class => [
FlushTemporaryContainerInstances::class,
// DisconnectFromDatabases::class,
// CollectGarbage::class,
FlushSpatieOnce::class, // we should create this class we have added here
],
And create the FlushSpatieOnce:class
:
// app/Listeners/FlushSpatieOnce.php
use Spatie\Once\Cache;
class FlushSpatieOnce
{
public function handle($event)
{
Cache::getInstance()->flush();
}
}
The once
function will execute the given callable and save the result in the $values
property of Spatie\Once\Cache
. This class is a singleton. When we detect that once
has already run before, we're just going to return the value stored inside the $values
weakmap instead of executing the callable again.
The first thing it does is calling debug_backtrace
. We'll use the output to determine in which function and class once
is called and to get access to the object
that function is running in. Yeah, we're already in voodoo-land. The output of the debug_backtrace
is passed to a new instance of Backtrace
. That class is just a simple wrapper, so we can work more easily with the backtrace.
$trace = debug_backtrace(
DEBUG_BACKTRACE_PROVIDE_OBJECT, 2
)[1];
$backtrace = new Backtrace($trace);
$object = $backtrace->getObject();
Next, we calculate a hash
of the backtrace. This hash will be unique per function once
was called in and the values of the arguments that function receives.
$hash = $backtrace->getHash();
Finally, we will check if there's already a value stored for the given hash. If not, then execute the given $callback
and store the result in the weakmap of Spatie\Once\Cache
. In the other case, we just return the value from that cache (the $callback
isn't executed).
public function has(object $object, string $backtraceHash): bool
{
if (! isset($this->values[$object])) {
return false;
}
return array_key_exists($backtraceHash, $this->values[$object]);
}
Please see CHANGELOG for more information what has changed recently.
composer test
Please see CONTRIBUTING for details.
If you've found a bug regarding security please mail [email protected] instead of using the issue tracker.
And a special thanks to Caneco for the logo โจ
Credit for the idea of the once
function goes to Taylor Otwell. The code for this package is based upon the code he was kind enough to share with us.
The MIT License (MIT). Please see License File for more information.