Autowire在Symfony的依赖注入组件中不起作用

Question

我在我的自定义PHP项目中使用Symfony的依赖注入组件3.4版。我的项目在PHP5.6上运行

"symfony/dependency-injection": "^3.4"

我已经将我的services.yaml文件定义为包含以下服务定义

logger:
  class: Monolog\Logger
  arguments: ["application"]
  autowire: true
  public: true

Monolog\Logger: '@logger'

plugin_context:
  class: MyProject\PluginContext
  autowire: true
  public: true

我可以确认自动加载正在工作，并且两个类的实例都存在于定义中，但是Logger类没有在PluginContext构造函数中自动连接。该类在以下代码中定义

use Monolog\Logger;

class PluginContext
{
    private $logger;
    function __construct(Logger $logger) {
        $this->logger = $logger;
    }
}

运行以下代码时，PHP将抛出异常

$container->get("plugin_context");

Catchable fatal error: Argument 1 passed to MyProject\PluginContext::__construct() must be an instance of Monolog\Logger, none given

Answer 1

改变你的FQCN $logger，用这个use Psr\Log\LoggerInterface代替Monolog\Logger另一个东西，多亏了自动装配，你不需要在service.yaml中指定任何东西，除了这个(默认配置)：

_defaults:
    autowire: true      # Automatically injects dependencies in your services.
    autoconfigure: true # Automatically registers your services as commands, event subscribers, etc.
    public: false       # Allows optimizing the container by removing unused services; this also means
                        # fetching services directly from the container via $container->get() won't work.
                        # The best practice is to be explicit about your dependencies anyway.

# makes classes in src/ available to be used as services
# this creates a service per class whose id is the fully-qualified class name
App\:
    resource: '../src/*'
    exclude: '../src/{Entity,Migrations,Tests,Kernel.php}'

Doc说：“核心捆绑包使用别名来允许服务自动连接。例如，MonologBundle创建了一个id为logger的服务。但它还添加了一个指向记录器服务的别名: Psr\Log\LoggerInterface。这就是使用Psr\Log\LoggerInterface类型提示的参数可以自动连接的原因。因此，在您的示例中，Psr\Log\LoggerInterface是Monolog https://symfony.com/doc/current/service_container/autowiring.html#using-aliases-to-enable-autowiring的别名

Answer 2

看起来services.yaml的内容都不是很满。

您的服务文件应如下所示

services:
  logger:
    class: Monolog\Logger
    arguments: ["application"]
    autowire: true
    public: true

  Monolog\Logger: '@logger'

  plugin_context:
    class: MyProject\PluginContext
    autowire: true
    public: true