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Oct 13, 2017
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some tweaks for the service locator chapter #8398

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some tweaks for the service locator chapter
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@xabbuh
xabbuh committed Sep 15, 2017
commit 47e28dd5d6aa8ffd998a8f981db5c486bf24f92b
48 changes: 27 additions & 21 deletions service_container/service_locators.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,9 @@ A real-world example are applications that implement the `Command pattern`_
using a CommandBus to map command handlers by Command class names and use them
to handle their respective command when it is asked for::

// src/AppBundle/CommandBus.php
namespace AppBundle;

// ...
class CommandBus
{
Expand Down Expand Up @@ -46,28 +49,29 @@ Considering that only one command is handled at a time, instantiating all the
other command handlers is unnecessary. A possible solution to lazy-load the
handlers could be to inject the whole dependency injection container::

use Symfony\Component\DependencyInjection\ContainerInterface;
// ...
use Symfony\Component\DependencyInjection\ContainerInterface;

class CommandBus
{
private $container;
class CommandBus
{
private $container;

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

public function handle(Command $command)
{
$commandClass = get_class($command);
public function handle(Command $command)
{
$commandClass = get_class($command);

if ($this->container->has($commandClass)) {
$handler = $this->container->get($commandClass);
if ($this->container->has($commandClass)) {
$handler = $this->container->get($commandClass);

return $handler->handle($command);
}
return $handler->handle($command);
}
}
}

However, injecting the entire container is discouraged because it gives too
broad access to existing services and it hides the actual dependencies of the
Expand All @@ -87,8 +91,8 @@ option to include as many services as needed to it and add the

.. code-block:: yaml

// app/config/services.yml
services:

app.command_handler_locator:
class: Symfony\Component\DependencyInjection\ServiceLocator
tags: ['container.service_locator']
Expand All @@ -99,6 +103,7 @@ option to include as many services as needed to it and add the

.. code-block:: xml

<!-- app/config/services.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
Expand All @@ -119,6 +124,7 @@ option to include as many services as needed to it and add the

.. code-block:: php

// app/config/services.php
use Symfony\Component\DependencyInjection\ServiceLocator;
use Symfony\Component\DependencyInjection\Reference;

Expand All @@ -144,13 +150,14 @@ Now you can use the service locator injecting it in any other service:

.. code-block:: yaml

// app/config/services.yml
services:

AppBundle\CommandBus:
arguments: ['@app.command_handler_locator']

.. code-block:: xml

<!-- app/config/services.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
Expand All @@ -159,19 +166,18 @@ Now you can use the service locator injecting it in any other service:
<services>

<service id="AppBundle\CommandBus">
<argument type="service" id="app.command_handler.locator" />
<argument type="service" id="app.command_handler_locator" />
</service>

</services>
</container>

.. code-block:: php

// app/config/services.php
use AppBundle\CommandBus;
use Symfony\Component\DependencyInjection\Reference;

//...

$container
->register(CommandBus::class)
->setArguments(array(new Reference('app.command_handler_locator')))
Expand All @@ -185,7 +191,7 @@ Now you can use the service locator injecting it in any other service:
Usage
-----

Back to the previous CommandBus example, it looks like this when using the
Back to the previous ``CommandBus`` example, it looks like this when using the
service locator::

// ...
Expand Down