How to Make Commands Lazily Loaded

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How to Make Commands Lazily Loaded

Note

If you are using the Symfony full-stack framework, you are probably looking for details about creating lazy commands

The traditional way of adding commands to your application is to use add(), which expects a Command instance as an argument.

In order to lazy-load commands, you need to register an intermediate loader which will be responsible for returning Command instances:

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use App\Command\HeavyCommand;
use Symfony\Component\Console\Application;
use Symfony\Component\Console\Command\Command;
use Symfony\Component\Console\CommandLoader\FactoryCommandLoader;

$commandLoader = new FactoryCommandLoader([
    'app:heavy' => function (): Command { return new HeavyCommand(); },
]);

$application = new Application();
$application->setCommandLoader($commandLoader);
$application->run();

This way, the HeavyCommand instance will be created only when the app:heavy command is actually called.

This example makes use of the built-in FactoryCommandLoader class, but the setCommandLoader() method accepts any CommandLoaderInterface instance so you can use your own implementation.

Built-in Command Loaders

FactoryCommandLoader

The FactoryCommandLoader class provides a way of getting commands lazily loaded as it takes an array of Command factories as its only constructor argument:

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use Symfony\Component\Console\Command\Command;
use Symfony\Component\Console\CommandLoader\FactoryCommandLoader;

$commandLoader = new FactoryCommandLoader([
    'app:foo' => function (): Command { return new FooCommand(); },
    'app:bar' => [BarCommand::class, 'create'],
]);

Factories can be any PHP callable and will be executed each time get() is called.

ContainerCommandLoader

The ContainerCommandLoader class can be used to load commands from a PSR-11 container. As such, its constructor takes a PSR-11 ContainerInterface implementation as its first argument and a command map as its last argument. The command map must be an array with command names as keys and service identifiers as values:

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use Symfony\Component\Console\CommandLoader\ContainerCommandLoader;
use Symfony\Component\DependencyInjection\ContainerBuilder;

$container = new ContainerBuilder();
$container->register(FooCommand::class, FooCommand::class);
$container->compile();

$commandLoader = new ContainerCommandLoader($container, [
    'app:foo' => FooCommand::class,
]);

Like this, executing the app:foo command will load the FooCommand service by calling $container->get(FooCommand::class).

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.
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