发布于 2015-08-27 16:52:13 | 199 次阅读 | 评论: 0 | 来源: 网络整理
As you add more functionality to your application, you may well start to have related classes that share some of the same dependencies. For example you may have a Newsletter Manager which uses setter injection to set its dependencies:
class NewsletterManager
{
protected $mailer;
protected $emailFormatter;
public function setMailer(Mailer $mailer)
{
$this->mailer = $mailer;
}
public function setEmailFormatter(EmailFormatter $emailFormatter)
{
$this->emailFormatter = $emailFormatter;
}
// ...
}
and also a Greeting Card class which shares the same dependencies:
class GreetingCardManager
{
protected $mailer;
protected $emailFormatter;
public function setMailer(Mailer $mailer)
{
$this->mailer = $mailer;
}
public function setEmailFormatter(EmailFormatter $emailFormatter)
{
$this->emailFormatter = $emailFormatter;
}
// ...
}
The service config for these classes would look something like this:
services:
my_mailer:
# ...
my_email_formatter:
# ...
newsletter_manager:
class: NewsletterManager
calls:
- [setMailer, ["@my_mailer"]]
- [setEmailFormatter, ["@my_email_formatter"]]
greeting_card_manager:
class: "GreetingCardManager"
calls:
- [setMailer, ["@my_mailer"]]
- [setEmailFormatter, ["@my_email_formatter"]]
<?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="my_mailer">
<!-- ... -->
</service>
<service id="my_email_formatter">
<!-- ... -->
</service>
<service id="newsletter_manager" class="NewsletterManager">
<call method="setMailer">
<argument type="service" id="my_mailer" />
</call>
<call method="setEmailFormatter">
<argument type="service" id="my_email_formatter" />
</call>
</service>
<service id="greeting_card_manager" class="GreetingCardManager">
<call method="setMailer">
<argument type="service" id="my_mailer" />
</call>
<call method="setEmailFormatter">
<argument type="service" id="my_email_formatter" />
</call>
</service>
</services>
</container>
use SymfonyComponentDependencyInjectionReference;
// ...
$container->register('my_mailer', ...);
$container->register('my_email_formatter', ...);
$container
->register('newsletter_manager', 'NewsletterManager')
->addMethodCall('setMailer', array(
new Reference('my_mailer'),
))
->addMethodCall('setEmailFormatter', array(
new Reference('my_email_formatter'),
))
;
$container
->register('greeting_card_manager', 'GreetingCardManager')
->addMethodCall('setMailer', array(
new Reference('my_mailer'),
))
->addMethodCall('setEmailFormatter', array(
new Reference('my_email_formatter'),
))
;
There is a lot of repetition in both the classes and the configuration. This
means that if you changed, for example, the Mailer of EmailFormatter
classes to be injected via the constructor, you would need to update the config
in two places. Likewise if you needed to make changes to the setter methods
you would need to do this in both classes. The typical way to deal with the
common methods of these related classes would be to extract them to a super class:
abstract class MailManager
{
protected $mailer;
protected $emailFormatter;
public function setMailer(Mailer $mailer)
{
$this->mailer = $mailer;
}
public function setEmailFormatter(EmailFormatter $emailFormatter)
{
$this->emailFormatter = $emailFormatter;
}
// ...
}
The NewsletterManager and GreetingCardManager can then extend this
super class:
class NewsletterManager extends MailManager
{
// ...
}
and:
class GreetingCardManager extends MailManager
{
// ...
}
In a similar fashion, the Symfony service container also supports extending services in the configuration so you can also reduce the repetition by specifying a parent for a service.
# ...
services:
# ...
mail_manager:
abstract: true
calls:
- [setMailer, ["@my_mailer"]]
- [setEmailFormatter, ["@my_email_formatter"]]
newsletter_manager:
class: "NewsletterManager"
parent: mail_manager
greeting_card_manager:
class: "GreetingCardManager"
parent: mail_manager
<?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="mail_manager" abstract="true">
<call method="setMailer">
<argument type="service" id="my_mailer" />
</call>
<call method="setEmailFormatter">
<argument type="service" id="my_email_formatter" />
</call>
</service>
<service
id="newsletter_manager"
class="NewsletterManager"
parent="mail_manager" />
<service
id="greeting_card_manager"
class="GreetingCardManager"
parent="mail_manager" />
</services>
</container>
use SymfonyComponentDependencyInjectionDefinition;
use SymfonyComponentDependencyInjectionDefinitionDecorator;
use SymfonyComponentDependencyInjectionReference;
// ...
$mailManager = new Definition();
$mailManager
->setAbstract(true);
->addMethodCall('setMailer', array(
new Reference('my_mailer'),
))
->addMethodCall('setEmailFormatter', array(
new Reference('my_email_formatter'),
))
;
$container->setDefinition('mail_manager', $mailManager);
$newsletterManager = new DefinitionDecorator('mail_manager');
$newsletterManager->setClass('NewsletterManager');
$container->setDefinition('newsletter_manager', $newsletterManager);
$greetingCardManager = new DefinitionDecorator('mail_manager');
$greetingCardManager->setClass('GreetingCardManager');
$container->setDefinition('greeting_card_manager', $greetingCardManager);
In this context, having a parent service implies that the arguments and
method calls of the parent service should be used for the child services.
Specifically, the setter methods defined for the parent service will be called
when the child services are instantiated.
注解
If you remove the parent config key, the services will still be instantiated
and they will still of course extend the MailManager class. The difference
is that omitting the parent config key will mean that the calls
defined on the mail_manager service will not be executed when the
child services are instantiated.
警告
The scope, abstract and tags attributes are always taken from
the child service.
The parent service is abstract as it should not be directly retrieved from the
container or passed into another service. It exists merely as a “template” that
other services can use. This is why it can have no class configured which
would cause an exception to be raised for a non-abstract service.
注解
In order for parent dependencies to resolve, the ContainerBuilder must
first be compiled. See Compiling the Container
for more details.
小技巧
In the examples shown, the classes sharing the same configuration also extend from the same parent class in PHP. This isn’t necessary at all. You can just extract common parts of similar service definitions into a parent service without also extending a parent class in PHP.
There may be times where you want to override what class is passed in for
a dependency of one child service only. Fortunately, by adding the method
call config for the child service, the dependencies set by the parent class
will be overridden. So if you needed to pass a different dependency just
to the NewsletterManager class, the config would look like this:
# ...
services:
# ...
my_alternative_mailer:
# ...
mail_manager:
abstract: true
calls:
- [setMailer, ["@my_mailer"]]
- [setEmailFormatter, ["@my_email_formatter"]]
newsletter_manager:
class: "NewsletterManager"
parent: mail_manager
calls:
- [setMailer, ["@my_alternative_mailer"]]
greeting_card_manager:
class: "GreetingCardManager"
parent: mail_manager
<?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="my_alternative_mailer">
<!-- ... -->
</service>
<service id="mail_manager" abstract="true">
<call method="setMailer">
<argument type="service" id="my_mailer" />
</call>
<call method="setEmailFormatter">
<argument type="service" id="my_email_formatter" />
</call>
</service>
<service
id="newsletter_manager"
class="NewsletterManager"
parent="mail_manager">
<call method="setMailer">
<argument type="service" id="my_alternative_mailer" />
</call>
</service>
<service
id="greeting_card_manager"
class="GreetingCardManager"
parent="mail_manager" />
</services>
</container>
use SymfonyComponentDependencyInjectionDefinition;
use SymfonyComponentDependencyInjectionDefinitionDecorator;
use SymfonyComponentDependencyInjectionReference;
// ...
$container->setDefinition('my_alternative_mailer', ...);
$mailManager = new Definition();
$mailManager
->setAbstract(true);
->addMethodCall('setMailer', array(
new Reference('my_mailer'),
))
->addMethodCall('setEmailFormatter', array(
new Reference('my_email_formatter'),
))
;
$container->setDefinition('mail_manager', $mailManager);
$newsletterManager = new DefinitionDecorator('mail_manager');
$newsletterManager->setClass('NewsletterManager');
->addMethodCall('setMailer', array(
new Reference('my_alternative_mailer'),
))
;
$container->setDefinition('newsletter_manager', $newsletterManager);
$greetingCardManager = new DefinitionDecorator('mail_manager');
$greetingCardManager->setClass('GreetingCardManager');
$container->setDefinition('greeting_card_manager', $greetingCardManager);
The GreetingCardManager will receive the same dependencies as before,
but the NewsletterManager will be passed the my_alternative_mailer
instead of the my_mailer service.
警告
You can’t override method calls. When you defined new method calls in the child
service, it’ll be added to the current set of configured method calls. This means
it works perfectly when the setter overrides the current property, but it doesn’t
work as expected when the setter appends it to the existing data (e.g. an
addFilters() method).
In those cases, the only solution is to not extend the parent service and configuring
the service just like you did before knowing this feature.