Why Lazy Services?¶
In some cases, you may want to inject a service that is a bit heavy to instantiate,
but is not always used inside your object. For example, imagine you have
NewsletterManager and you inject a
mailer service into it. Only
a few methods on your
NewsletterManager actually use the
but even when you don't need it, a
mailer service is always instantiated
in order to construct your
Configuring lazy services is one answer to this. With a lazy service, a
"proxy" of the
mailer service is actually injected. It looks and acts
just like the
mailer, except that the
mailer isn't actually instantiated
until you interact with the proxy in some way.
In order to use the lazy service instantiation, you will first need to install the ProxyManager bridge:
$ composer require symfony/proxy-manager-bridge
If you're using the full-stack framework, the proxy manager bridge is already included but the actual proxy manager needs to be included. So, run:
$ composer require ocramius/proxy-manager:~1.0
Afterwards compile your container and check to make sure that you get a proxy for your lazy services.
You can mark the service as
lazy by manipulating its definition:
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services: foo: class: Acme\Foo lazy: true
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<?xml version="1.0" encoding="UTF-8" ?> <container xmlns="http://symfony.com/schema/dic/services" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd"> <services> <service id="foo" class="Acme\Foo" lazy="true" /> </services> </container>
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use Symfony\Component\DependencyInjection\Definition; $definition = new Definition('Acme\Foo'); $definition->setLazy(true); $container->setDefinition('foo', $definition);
You can then require the service from the container:
$service = $container->get('foo');
At this point the retrieved
$service should be a virtual proxy with
the same signature of the class representing the service. You can also inject
the service just like normal into other services. The object that's actually
injected will be the proxy.
To check if your proxy works you can simply check the interface of the received object.
If the class implements the
your lazy loaded services are working.
If you don't install the ProxyManager bridge, the container will
just skip over the
lazy flag and simply instantiate the service
as it would normally do.
The proxy gets initialized and the actual service is instantiated as soon as you interact in any way with this object.
This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.