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Improve your factories in Symfony

Marc Guinea on March 03, 2022

Sometimes we need to retrieve some kind of handler class that depending on an attribute is different. Thanks to Factory pattern we can solve this ...
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vasilvestre profile image
Valentin Silvestre • • Edited

I love this pattern ! It's really clean.
You could even simplify it using tagged_iterator.

_instanceof:
        App\ChannelHandlerInterface:
            tags: ['app.channel_handler']

App\ChannelFactory:
    arguments:
      - !tagged_iterator app.channel_handler
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Thanks to DI feature, you do not have to declare anything manually !

The idea come from Thibault Richard (github.com/t-richard) :)

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mguinea profile image
Marc Guinea •

Wow! looks awesome! even better, thanks for sharing

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vasilvestre profile image
Valentin Silvestre •

I think you could update your post with it ;)

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mguinea profile image
Marc Guinea •

Done! many thanks :)

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aheiland profile image
Andreas Rau • • Edited

How about?

final class ChannelFactory
{
    /** @var array<string, ChannelInterface> */
    private array $lookUp = [];

    public function __construct(...ChannelInterface channels)
    {
        foreach($channels as $channel) {
            $this->lookUp[$channel->getType()] = $channel;
        }
    }

    public function create(string $type): ChannelInteface
    {
        if (!array_key_exists($type, $this->lookUp)) {
            throw new InvalidArgumentException('Unknown channel given');
        }
        return $this->lookUp[$type];
    }
}
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Alessandro GIULIANI • • Edited

And this one ? ^^

final class ChannelFactory
{
    /** @var array<string, ChannelInterface> */
    private array $lookUp;

    public function __construct(ChannelInterface ...$channels)
    {
        $this->lookUp = array_combine(array_column($channels, 'type'), $channels);
    }

    public function create(string $type): ChannelInteface
    {
        return $this->lookUp[$type] ?? throw new InvalidArgumentException('Unknown channel given');
    }
}
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tomasvotruba profile image
Tomáš Votruba •

You can also take it one step further, avoid tags and any YAML coding by using annotation autowire:

final class ChannelFactory
{
    /**
     * @param ChannelInterface[] $channels
     */
    public function __construct(private array $channels)
    {
    }

    // ...
}
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mguinea profile image
Marc Guinea •

Yep, but then you are placing something from the Framework (infrastructure layer) to the factory (domain layer).

It's also a valid approach, but I prefer keeping things separated (depends on the architecture of your app, of course).

Anyway, thanks for the idea!

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fd6130 profile image
fd6130 • • Edited

Hi, how do you use those class property in a static method? I try to call $this->channels and my IDE show error Cannot use '$this' in non-object context.

And do I still need to inject the factory class or I can just directly use it like ChannelFactory::create()?

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mguinea profile image
Marc Guinea •

This was an error! just fixed... this shouldn't be a static class, we want to use service container to manage that data. Thanks & fixed!

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dziugasdraksas profile image
DziugasDraksas •

I would suggest minor optimization.
Do not create new $channel, since all channels are already initialized.
Just return it:

foreach($this->channels as $channel) {
    if ($type === $channel::getType()) {
        return $channel;
     }
}
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