How to set Rails engine locale (it's using :en even tough host app has a different locale)

Question

I followed the great Rails guide on engines ( https://guides.rubyonrails.org/engines.html ) and managed to get my engine working in a host app.

However, the engine is loading only the en.yml locale, even tough the host application has I18n.default_locale and I18n.locale both set to pt-br , and I have a config/locales/pt-br.yml file in my engine.

The guide only states that "For locales, simply place the locale files in the config/locales directory, just like you would in an application.", but apparently I need to do something else.

How would I make the engine to load the correct I18n locale files, based on the host app settings? If that's not possible, how the host app could set this locale in an initializer file, like a config option?

Answer 1

I managed to solve it. The key is to remember that I18n.locale is a setting that should be set on every request.

So on my engine entry point ( lib/cron_monitor.rb ), I defined a setting:

module CronMonitor

  class << self

    attr_accessor :i18n

  end

  self.i18n = I18n.default_locale

Then in my engine's ApplicationController , following Rails i18n documentation :

module CronMonitor
  class ApplicationController < ActionController::Base
    around_action :switch_locale

    private

    def switch_locale(&action)
      locale = CronMonitor.i18n || I18n.default_locale
      I18n.with_locale(locale, &action)
    end

  end
end

Also, if you have code in models or service objects that you also want to be translated, you should use I18n as well. Example:

module CronMonitor
  class Category < ApplicationRecord

  def self.some_method

        message = I18n.translate(
          "cron_monitor.starting_or_finishing.failure",
          title: self.title,
          locale: CronMonitor.i18n
        )
  end

end