How can I send emails in Rails 3 using the recipient's locale?

How can I send mails in a mailer using the recipient's locale. I have the preferred locale for each user in the database. Notice this is different from the current locale (I18n.locale), as long as the current user doesn't have to be the recipient. So the difficult thing is to use the mailer in a different locale without changing I18n.lo开发者_如何转开发cale:

def new_follower(user, follower)
  @follower = follower
  @user = user
  mail :to=>@user.email
end

Using I18n.locale = @user.profile.locale before mail :to=>... would solve the mailer issue, but would change the behaviour in the rest of the thread.

I believe the best way to do this is with the great method I18n.with_locale, it allows you to temporarily change the I18n.locale inside a block, you can use it like this:

def new_follower(user, follower)
  @follower = follower
  @user = user
  I18n.with_locale(@user.profile.locale) do
    mail to: @user.email
  end
end

And it'll change the locale just to send the email, immediately changing back after the block ends.

Source: http://www.rubydoc.info/docs/rails/2.3.8/I18n.with_locale

This answer was a dirty hack that ignored I18n's with_locale method, which is in another answer. The original answer (which works but you shouldn't use it) is below.

Quick and dirty:

class SystemMailer < ActionMailer::Base
  def new_follower(user, follower)
    @follower = follower
    @user = user
    using_locale(@user.profile.locale){mail(:to=>@user.email)}
  end

  protected
  def using_locale(locale, &block)
    original_locale = I18n.locale
    I18n.locale = locale
    return_value = yield
    I18n.locale = original_locale
    return_value
  end
end

in the most resent version of rails at this time it's sufficient to use "I18n.locale = account.locale" in the controller and make multiple views with the following naming strategy welcome.html.erb, welcome.it.html.erb and e.g. welcome.fr.html.erb

None of the above is really working since the version 3 to translate both subject and content and be sure that the locale is reseted back to the original one... so I did the following (all mailer inherit from that class:

class ResourceMailer < ActionMailer::Base

  def mail(headers={}, &block)
    I18n.locale = mail_locale
    super
  ensure
    reset_locale
  end

  def i18n_subject(options = {})
    I18n.locale = mail_locale
    mailer_scope = self.class.mailer_name.gsub('/', '.')
    I18n.t(:subject, options.merge(:scope => [mailer_scope, action_name], :default => action_name.humanize))
  ensure
    reset_locale
  end  

  def set_locale(locale)
    @mail_locale = locale
  end

  protected

  def mail_locale
    @mail_locale || I18n.locale
  end

  def reset_locale
    I18n.locale = I18n.default_locale
  end

end

You just need to set the locale before you call the mail() method:

set_locale @user.locale

You can use the i18n_subject method which scope the current path so everything is structured:

mail(:subject => i18n_subject(:name => @user.name)

This simple plugin was developed for rails 2 but seems to work in rails 3 too.

http://github.com/Bertg/i18n_action_mailer

With it you can do the following:

def new_follower(user, follower)
  @follower = follower
  @user = user
  set_locale user.locale
  mail :to => @user.email, :subject => t(:new_follower_subject)
end

The subject and mail templates are then translated using the user's locale.

Here's an updated version that also supports the '.key' short-hand notation, so you don't have to spell out each key in its entirety.

http://github.com/larspind/i18n_action_mailer

The problem with the mentioned plugins are that they don't work in all situations, for example doing User.human_name or User.human_attribute_name(...) will not translate correctly. The following is the easiest and guaranteed method to work:

stick this somewhere (in initializers or a plugin):

  module I18nActionMailer
    def self.included(base)
      base.class_eval do
        include InstanceMethods
        alias_method_chain :create!, :locale
      end
    end

    module InstanceMethods
      def create_with_locale!(method_name, *parameters)
        original_locale = I18n.locale
        begin
          create_without_locale!(method_name, *parameters)
        ensure
          I18n.locale = original_locale
        end
      end
    end
  end

  ActionMailer::Base.send(:include, I18nActionMailer)

and then in your mailer class start your method by setting the desired locale, for example:

  def welcome(user)
    I18n.locale = user.locale
    # etc.
  end