I18n: How to check if a translation key/value pairs is missing? - ruby-on-rails

Question

I am using Ruby on Rails 3.1.0 and the I18n gem. I (am implementing a plugin and) I would like to check at runtime if the I18n is missing a translation key/value pairs and, if so, to use a custom string. That is, I have:
validates :link_url,
:format => {
:with => REGEX,
:message => I18n.t(
'custom_invalid_format',
:scope => 'activerecord.errors.messages'
)
}
If in the .yml file there is not the following code
activerecord:
errors:
messages:
custom_invalid_format: This is the test error message 1
I would like to use the This is the test error message 2. Is it possible? If so, how can I make that?
BTW: For performance reasons, is it advisable to check at runtime if the translation key/value pairs is present?

Answer 1

You could pass a :default parameter to I18n.t:
I18n.t :missing, :default => 'Not here'
# => 'Not here'
You can read more about it here.

Answer 2

I just had the same question and I want to compute an automatic string in case the translation is missing. If I use the :default option I have to compute the automatic string every time even when the translation is not missing. So I searched for another solution.
You can add the option :raise => true or use I18n.translate! instead of I18n.translate. If no translation can be found an exception is raised.
begin
I18n.translate!('this.key.should.be.translated', :raise => true)
rescue I18n::MissingTranslationData
do_some_resource_eating_text_generation_here
end

Answer 3

I don't know how to this at runtime but you can use rake to find it out. You'll have create your own rake task for that. Here's one:
namespace :i18n do
desc "Find and list translation keys that do not exist in all locales"
task :missing_keys => :environment do
def collect_keys(scope, translations)
full_keys = []
translations.to_a.each do |key, translations|
new_scope = scope.dup << key
if translations.is_a?(Hash)
full_keys += collect_keys(new_scope, translations)
else
full_keys << new_scope.join('.')
end
end
return full_keys
end
# Make sure we've loaded the translations
I18n.backend.send(:init_translations)
puts "#{I18n.available_locales.size} #{I18n.available_locales.size == 1 ? 'locale' : 'locales'} available: #{I18n.available_locales.to_sentence}"
# Get all keys from all locales
all_keys = I18n.backend.send(:translations).collect do |check_locale, translations|
collect_keys([], translations).sort
end.flatten.uniq
puts "#{all_keys.size} #{all_keys.size == 1 ? 'unique key' : 'unique keys'} found."
missing_keys = {}
all_keys.each do |key|
I18n.available_locales.each do |locale|
I18n.locale = locale
begin
result = I18n.translate(key, :raise => true)
rescue I18n::MissingInterpolationArgument
# noop
rescue I18n::MissingTranslationData
if missing_keys[key]
missing_keys[key] << locale
else
missing_keys[key] = [locale]
end
end
end
end
puts "#{missing_keys.size} #{missing_keys.size == 1 ? 'key is missing' : 'keys are missing'} from one or more locales:"
missing_keys.keys.sort.each do |key|
puts "'#{key}': Missing from #{missing_keys[key].join(', ')}"
end
end
end
put the given in a .rake file in your lib/tasks directory and execute:
rake i18n:missing_keys
Information source is here and code on github here.

Answer 4

If you wish to pass variable to the message like This is the test error message {variable}
This is possible using variable in language file like below.
# app/views/home/index.html.erb
<%=t 'greet_username', :user => "Bill", :message => "Goodbye" %>
# config/locales/en.yml
en:
greet_username: "%{message}, %{user}!"
More description you can find here.