即使服务缺少依赖性，服务也不会被忽略

Question

我有一个服务定义，如下所示：

app.logging.event_subscriber.my_subscriber:
    class: AppBundle\Event\Subscriber\MySubscriber
    arguments:
        - '@?app.logging.optional_dependency'
    tags:
        - { name: kernel.event_subscriber }

如果缺少“app.logging.optional_dependency”服务，则不应定义我的服务“app.logging.event_subscriber.my_subscriber”，但我得到例外：

TypeError: Argument 1 passed to AppBundle\Event\Subscriber\MySubscriber::__construct() must be an instance of AppBundle\Logging\OptionalDependency, null given, called in /app/app/cache/test/appTestProjectContainer.php on line 936

Answer 1

为构造函数null

的参数添加默认值AppBundle\Event\Subscriber\MySubscriber

public function __constructor (OptionalDependency $dependency = null)