Using Parameters within a Dependency Injection Class
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You have seen how to use configuration parameters within
Symfony service containers.
There are special cases such as when you want, for instance, to use the
%kernel.debug%
parameter to make the services in your bundle enter
debug mode. For this case there is more work to do in order
to make the system understand the parameter value. By default,
your parameter %kernel.debug%
will be treated as a string. Consider the
following example:
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// inside Configuration class
$rootNode
->children()
->booleanNode('logging')->defaultValue('%kernel.debug%')->end()
// ...
->end()
;
// inside the Extension class
$config = $this->processConfiguration($configuration, $configs);
var_dump($config['logging']);
Now, examine the results to see this closely:
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my_bundle:
logging: true
# true, as expected
my_bundle:
logging: '%kernel.debug%'
# true/false (depends on 2nd argument of the Kernel class),
# as expected, because %kernel.debug% inside configuration
# gets evaluated before being passed to the extension
my_bundle: ~
# passes the string "%kernel.debug%".
# Which is always considered as true.
# The Configurator does not know anything about
# "%kernel.debug%" being a parameter.
In order to support this use case, the Configuration
class has to
be injected with this parameter via the extension as follows:
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namespace App\DependencyInjection;
use Symfony\Component\Config\Definition\Builder\TreeBuilder;
use Symfony\Component\Config\Definition\ConfigurationInterface;
class Configuration implements ConfigurationInterface
{
private $debug;
public function __construct($debug)
{
$this->debug = (bool) $debug;
}
public function getConfigTreeBuilder()
{
$treeBuilder = new TreeBuilder('my_bundle');
$treeBuilder->getRootNode()
->children()
// ...
->booleanNode('logging')->defaultValue($this->debug)->end()
// ...
->end()
;
return $treeBuilder;
}
}
And set it in the constructor of Configuration
via the Extension
class:
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namespace App\DependencyInjection;
use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\HttpKernel\DependencyInjection\Extension;
class AppExtension extends Extension
{
// ...
public function getConfiguration(array $config, ContainerBuilder $container)
{
return new Configuration($container->getParameter('kernel.debug'));
}
}
Tip
There are some instances of %kernel.debug%
usage within a
Configurator
class for example in TwigBundle. However, this is because
the default parameter value is set by the Extension class.