发布于 2015-08-27 16:46:45 | 126 次阅读 | 评论: 0 | 来源: 网络整理
Tags are a generic string (along with some options) that can be applied to any service. By themselves, tags don’t actually alter the functionality of your services in any way. But if you choose to, you can ask a container builder for a list of all services that were tagged with some specific tag. This is useful in compiler passes where you can find these services and use or modify them in some specific way.
For example, if you are using Swift Mailer you might imagine that you want
to implement a “transport chain”, which is a collection of classes implementing
Swift_Transport. Using the chain, you’ll want Swift Mailer to try several
ways of transporting the message until one succeeds.
To begin with, define the TransportChain class:
class TransportChain
{
private $transports;
public function __construct()
{
$this->transports = array();
}
public function addTransport(Swift_Transport $transport)
{
$this->transports[] = $transport;
}
}
Then, define the chain as a service:
services:
acme_mailer.transport_chain:
class: TransportChain
<?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="acme_mailer.transport_chain" class="TransportChain" />
</services>
</container>
use SymfonyComponentDependencyInjectionDefinition;
$container->setDefinition('acme_mailer.transport_chain', new Definition('TransportChain'));
Now you might want several of the Swift_Transport classes to be instantiated
and added to the chain automatically using the addTransport() method.
For example you may add the following transports as services:
services:
acme_mailer.transport.smtp:
class: Swift_SmtpTransport
arguments:
- "%mailer_host%"
tags:
- { name: acme_mailer.transport }
acme_mailer.transport.sendmail:
class: Swift_SendmailTransport
tags:
- { name: acme_mailer.transport }
<?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="acme_mailer.transport.smtp" class="Swift_SmtpTransport">
<argument>%mailer_host%</argument>
<tag name="acme_mailer.transport" />
</service>
<service id="acme_mailer.transport.sendmail" class="Swift_SendmailTransport">
<tag name="acme_mailer.transport" />
</service>
</services>
</container>
use SymfonyComponentDependencyInjectionDefinition;
$definitionSmtp = new Definition('Swift_SmtpTransport', array('%mailer_host%'));
$definitionSmtp->addTag('acme_mailer.transport');
$container->setDefinition('acme_mailer.transport.smtp', $definitionSmtp);
$definitionSendmail = new Definition('Swift_SendmailTransport');
$definitionSendmail->addTag('acme_mailer.transport');
$container->setDefinition('acme_mailer.transport.sendmail', $definitionSendmail);
Notice that each was given a tag named acme_mailer.transport. This is
the custom tag that you’ll use in your compiler pass. The compiler pass
is what makes this tag “mean” something.
CompilerPass¶Your compiler pass can now ask the container for any services with the custom tag:
use SymfonyComponentDependencyInjectionContainerBuilder;
use SymfonyComponentDependencyInjectionCompilerCompilerPassInterface;
use SymfonyComponentDependencyInjectionReference;
class TransportCompilerPass implements CompilerPassInterface
{
public function process(ContainerBuilder $container)
{
if (!$container->has('acme_mailer.transport_chain')) {
return;
}
$definition = $container->findDefinition(
'acme_mailer.transport_chain'
);
$taggedServices = $container->findTaggedServiceIds(
'acme_mailer.transport'
);
foreach ($taggedServices as $id => $tags) {
$definition->addMethodCall(
'addTransport',
array(new Reference($id))
);
}
}
}
The process() method checks for the existence of the acme_mailer.transport_chain
service, then looks for all services tagged acme_mailer.transport. It adds
to the definition of the acme_mailer.transport_chain service a call to
addTransport() for each “acme_mailer.transport” service it has found.
The first argument of each of these calls will be the mailer transport service
itself.
You also need to register the pass with the container, it will then be run when the container is compiled:
use SymfonyComponentDependencyInjectionContainerBuilder;
$container = new ContainerBuilder();
$container->addCompilerPass(new TransportCompilerPass());
注解
Compiler passes are registered differently if you are using the full stack framework. See How to Work with Compiler Passes in Bundles for more details.
Sometimes you need additional information about each service that’s tagged with your tag. For example, you might want to add an alias to each member of the transport chain.
To begin with, change the TransportChain class:
class TransportChain
{
private $transports;
public function __construct()
{
$this->transports = array();
}
public function addTransport(Swift_Transport $transport, $alias)
{
$this->transports[$alias] = $transport;
}
public function getTransport($alias)
{
if (array_key_exists($alias, $this->transports)) {
return $this->transports[$alias];
}
}
}
As you can see, when addTransport is called, it takes not only a Swift_Transport
object, but also a string alias for that transport. So, how can you allow
each tagged transport service to also supply an alias?
To answer this, change the service declaration:
services:
acme_mailer.transport.smtp:
class: Swift_SmtpTransport
arguments:
- "%mailer_host%"
tags:
- { name: acme_mailer.transport, alias: foo }
acme_mailer.transport.sendmail:
class: Swift_SendmailTransport
tags:
- { name: acme_mailer.transport, alias: bar }
<?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="acme_mailer.transport.smtp" class="Swift_SmtpTransport">
<argument>%mailer_host%</argument>
<tag name="acme_mailer.transport" alias="foo" />
</service>
<service id="acme_mailer.transport.sendmail" class="Swift_SendmailTransport">
<tag name="acme_mailer.transport" alias="bar" />
</service>
</services>
</container>
use SymfonyComponentDependencyInjectionDefinition;
$definitionSmtp = new Definition('Swift_SmtpTransport', array('%mailer_host%'));
$definitionSmtp->addTag('acme_mailer.transport', array('alias' => 'foo'));
$container->setDefinition('acme_mailer.transport.smtp', $definitionSmtp);
$definitionSendmail = new Definition('Swift_SendmailTransport');
$definitionSendmail->addTag('acme_mailer.transport', array('alias' => 'bar'));
$container->setDefinition('acme_mailer.transport.sendmail', $definitionSendmail);
Notice that you’ve added a generic alias key to the tag. To actually
use this, update the compiler:
use SymfonyComponentDependencyInjectionContainerBuilder;
use SymfonyComponentDependencyInjectionCompilerCompilerPassInterface;
use SymfonyComponentDependencyInjectionReference;
class TransportCompilerPass implements CompilerPassInterface
{
public function process(ContainerBuilder $container)
{
if (!$container->hasDefinition('acme_mailer.transport_chain')) {
return;
}
$definition = $container->getDefinition(
'acme_mailer.transport_chain'
);
$taggedServices = $container->findTaggedServiceIds(
'acme_mailer.transport'
);
foreach ($taggedServices as $id => $tags) {
foreach ($tags as $attributes) {
$definition->addMethodCall(
'addTransport',
array(new Reference($id), $attributes["alias"])
);
}
}
}
}
The double loop may be confusing. This is because a service can have more than one
tag. You tag a service twice or more with the acme_mailer.transport tag. The
second foreach loop iterates over the acme_mailer.transport tags set for the
current service and gives you the attributes.