Symfony forcing translation into different language than the current one - symfony

Question

I have the locale set to one language. Let's say german "de" and I want to have a part of the whole text translated into different languages (Ex. This happened 100 years ago -> This happened vor 100 Jahre). For this I am trying the following code:
//this returns 'site.dates.years'
{% set yearsText = yearsCount|displayTimeDivisions() %}
( {{ yearsCount }} {% trans with {'%content%': yearsText } from "messages" into "en" %}%content%{% endtrans %}
after using the trans method i get the string from yearsText ('site.dates.years') and not the translated content. Is this even possible to translate or I should drop it?

Answer 1

This works as expected, what you are trying to translate is %content%, not site.dates.years. Try this:
//this returns 'site.dates.years'
{% set yearsText = yearsCount|displayTimeDivisions() %}
( {{ yearsCount }} {% trans from "messages" into "en" %}{{ yearsText }}{% endtrans %}
Edit
The previous suggestion doesn't work as using trans in that way only works with simple text, not with variables.
This works for me:
{{ yearsText | trans({}, 'messages', 'en') }}

Answer 2

EDIT: clear cache
Sometimes Symfony has a too strong caching mechanism. If you work without locales first, and then modify controllers and twigs to be multi-locale and you also add a new messages file, Symfony loads all new controller/twigs but somehow misses that there are new message files. A simple cache clear, done ONLY ONCE (!) right after you add the message files, solves this problem. And thenceforth you don't need to clear the cache every time you change a translation.
Try this as a last resort. If this doesn't help I'd recommend to read carefully the documentation (link in the last line of this answer):
app/console cache:clear --env=dev
You may try one or all (!) of these, it's impossible to tell what is going wrong.
{{ yearsCount|trans }}
{{ 'site.dates.years'|trans }}
See if these translate. If the second does, you're setting the variable wrong, somehow.
If not, pass the _locale along in the route:
defaults: { _controller: Bundle:Controller:action, _locale: de }
Or have it as a route parameter:
path: /a/path/{_locale}/whatever
defaults: { _controller: Bundle:Controller:action }
requirements:
_locale: en|de
Print the locale to be sure it's properly set in the twig:
{{ app.request.locale }}
{{ app.request.getLocale() }}
If the locale prints out fine but the translation still does not work, it's because Symfony does not find the identifier. Go to the translations file and check that it's written correctly:
site:
dates:
years: Jahre
If you find it in messages.de.yml then maybe it's the wrong placement of the file. The loader searches for these files:
Symfony looks for message files (i.e. translations) in the following default locations:
the app/Resources/translations directory;
the app/Resources/MyAppBundle/translations directory;
the Resources/translations/ directory inside of any bundle.
If fiddling around with these files doesn't yield results, it's a configuration error in config.yml, or many overlapping errors (all of the above?) that work against you.
Here's the source of all pain/info about translations, but you've probably memorized every paragraph, by now: Symfony translations.