Symfony2 依赖注入与父服务不起作用

Question

我目前正在尝试配置我的 Symfony 依赖注入，以便能够使用父服务。按照我在http://symfony.com/doc/current/components/dependency_injection/parentservices.html 中找到的描述，我尝试设置以下类作为第一个测试：

Mailer.php：

namespace testing;

class Mailer
{
    private $transport;

    public function __construct($transport) {
        $this->transport = $transport;
    }

    public function getTransport() {
        return $this->transport;
    }
}

MailManager.php：

namespace testing;

abstract class MailManager
{
    protected $mailer;

    public function setMailer(Mailer $mailer)
    {
         $this->mailer = $mailer;
    }
}

NewsletterManager.php：

namespace testing;

class NewsletterManager extends MailManager {
    function getTransport() {
        return $this->mailer->getTransport();
    }
}

services.yml：

 parameters:
    mailer.transport: sendmail

services:
    mailer:
        class:     testing\Mailer
        arguments: [%mailer.transport%]
    mail_manager:
        class:     testing\MailManager
        abstract:  true
        calls:
             - [ setMailer, [ @mailer ] ]
    newsletter_manager:
        class:     testing\NewsletterManager
        parent:    mail_manager

但是当我尝试使用以下代码运行此配置时：

require_once 'ClassLoading.php';
use Symfony\Component\Config\FileLocator;
use Symfony\Component\DependencyInjection\Loader\YamlFileLoader;
use Symfony\Component\DependencyInjection\ContainerBuilder;

$container = new ContainerBuilder();
$loader = new YamlFileLoader($container, new FileLocator(__DIR__.'/config'));
$loader->load('services.yml');

$nm = $container->get('newsletter_manager');
echo $nm->getTransport();

我总是收到这个错误：

PHP Fatal error:  Call to a member function getTransport() on a non-object in C:\IGMI\workspace\TryingHard\loading\NewsletterManager.php on line 7

一件事似乎是抽象类的setter从未被调用，但即使我将抽象类具体化并从容器中检索它并实际调用setter，这并不能解决问题未设置邮件程序对象。所以在我看来，子类关系的建立也有问题。

任何帮助将不胜感激！

Answer 1

你应该在尝试访问服务之前编译容器构建器我认为...... 所以它应该看起来像：

use Symfony\Component\Config\FileLocator;
use Symfony\Component\DependencyInjection\Loader\YamlFileLoader;

use Symfony\Component\DependencyInjection\ContainerBuilder;

$container = new ContainerBuilder();
$loader = new YamlFileLoader($container, new FileLocator(__DIR__.'/config'));
$loader->load('services.yml');

$container->compile(); //add this line

$nm = $container->get('newsletter_manager');
echo $nm->getTransport();