Q:

symfony translation resources with custom domain doesn't load

I have a little problem.
When I add a custom domain to my resource for translation, it doesn't load.
My code working (no custom domain) :
$app['translator'] = $app->share($app->extend('translator', function ($translator, $app) {
    $translator->addLoader('yaml', new Symfony\Component\Translation\Loader\YamlFileLoader());

    $translator->addResource('yaml', __DIR__ . '/../views/backend/translator/translations/back-office.en_GB.yml', 'en_GB');
    $translator->addResource('yaml', __DIR__ . '/../views/backend/translator/translations/back-office.fr_FR.yml', 'fr_FR');

    return $translator;
}));

My code I want to do and not working :
$app['translator'] = $app->share($app->extend('translator', function ($translator, $app) {
    $translator->addLoader('yaml', new Symfony\Component\Translation\Loader\YamlFileLoader());

    $translator->addResource('yaml', __DIR__ . '/../views/backend/translator/translations/back-office.en_GB.yml', 'en_GB', 'back-office');
    $translator->addResource('yaml', __DIR__ . '/../views/backend/translator/translations/back-office.fr_FR.yml', 'fr_FR', 'back-office');

    return $translator;
}));

the default domain is "messages", how can I change it ?
regards
EDIT :
I just noticed that it doesn't load the other resource files. 
If I add empty file resource first then my translation resource file, translation doesn't appear on my twig files, it print the variable.
$translator->addResource('yaml', __DIR__ . '/../views/backend/translator/translations/messages.en_GB.yml', 'en_GB');
    $translator->addResource('yaml', __DIR__ . '/../views/backend/translator/translations/messages.fr_FR.yml', 'fr_FR');
    $translator->addResource('yaml', __DIR__ . '/../views/backend/translator/translations/back-office.en_GB.yml', 'en_GB', 'back-office');
    $translator->addResource('yaml', __DIR__ . '/../views/backend/translator/translations/back-office.fr_FR.yml', 'fr_FR', 'back-office');

EDIT 2 :
I get it, I should specify the domain on each variable in the twig file or specify the default domain on each twig files :
{{ 'label.name'|trans({}, 'app') }}
or
{% trans_default_domain "app" %}
It's really not easy to manage when you have lot of files...

A:

I get it, I should specify the domain on each variable in the twig file or specify the default domain on each twig files :
{{ 'label.name'|trans({}, 'app') }}

or
{% trans_default_domain "app" %}

It's really not easy to manage when you have lot of files...

