05_Manual_Service_Wiring_And_Parameter_Building.md

Manual Service Wiring & Parameter Building

Manual Service Wiring

• a few cases exist when an argument to a service cannot be autowired
  • examples:
    • configurable admin email in the constructor of a service
    • configurable text message for a greeting service

Example: string argument in a constructor

• Add a string argument to the constructor of Greeting service

# src/Service/Greeting.php

namespace App\Service;

use Psr\Log\LoggerInterface;

class Greeting
{
    /**
     * @var LoggerInterface
     */
    private $logger;
    /**
     * @var string
     */
    private $message;

    /**
     * Greeting constructor.
     */
    public function __construct(LoggerInterface $logger, string $message)
    {
        $this->logger = $logger;
        $this->message = $message;
    }

    public function greet(string $name): string
    {
        $this->logger->info("Greeted $name");

        return "{$this->message} $name";
    }
}

• Refresh the page (/?name=Siven)
  • Error

Cannot autowire service "App\Service\Greeting": argument "$message" of method "__construct()" is type-hinted "string", you should configure its value explicitly.

• Define the service manually
  • In services.yaml, add an entry for the service and pass a value for the argument $message

App\Service\Greeting:
    arguments:
        $message: 'Hello from service'

Note

• by default autowire is already set to true in services.yaml

  • not necessary to specify the arguments for autowired services

• Refresh the page

  • Success: the page will now show Hello from service Siven

Service Parameters

• the container also holds configuration, called parameters, in addition to service objects
• to create a parameter:
  • add it under the parameters key
  • reference it with the %parameter_name%
  • it can be referenced in any other configuration file
  • many are defined in the config/services.yaml file

Example 1

# config/services.yaml
parameters:
    admin_email: manager@example.com

services:
    # ...

    App\Updates\SiteUpdateManager:
        arguments:
            $adminEmail: '%admin_email%'

The parameter can be fetched in the service as follows:

class SiteUpdateManager
{
    // ...

    private $adminEmail;

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

Parameters can also be fetched directly from the container:

public function new()
{
    // ...

    // this shortcut ONLY works if you extend the base AbstractController
    $adminEmail = $this->getParameter('admin_email');

    // this is the equivalent code of the previous shortcut:
    // $adminEmail = $this->container->get('parameter_bag')->get('admin_email');
}

Example 2

• Define a parameter for the string
  • In the services.yaml file, add the following line under parameters

parameters:
    locale: 'en'
    hello_message: 'Hello from service'

• Change the service definition to use the defined parameter

App\Service\Greeting:
    arguments:
        $message: '%hello_message%'

• Refresh the page
  • Success: the page still works

Binding Arguments by Name or Type

• the bind keyword can also be used to bind specific arguments by name or type

Example

# config/services.yaml
services:
    _defaults:
        bind:
            # pass this value to any $adminEmail argument for any service
            # that's defined in this file (including controller arguments)
            $adminEmail: 'manager@example.com'

            # pass this service to any $requestLogger argument for any
            # service that's defined in this file
            $requestLogger: '@monolog.logger.request'

            # pass this service for any LoggerInterface type-hint for any
            # service that's defined in this file
            Psr\Log\LoggerInterface: '@monolog.logger.request'

            # optionally you can define both the name and type of the argument to match
            string $adminEmail: 'manager@example.com'
            Psr\Log\LoggerInterface $requestLogger: '@monolog.logger.request'

    # ...

• bind key under _defaults
  • specify the value of any argument for any service defined in that file
  • bind arguments
    • by name (e.g. $adminEmail),
    • by type (e.g.. Psr\Log\LoggerInterface), or
    • both (e.g. Psr\Log\LoggerInterface $requestLogger)