Flash messages in Rails applications need a bit of love. A lot of them tend to be identical within a given app, and it’s a bit annoying to manage defaults and fallback for all these calls to I18n.t(). The following is a small helper-method and a simple structure to keep it all neatly organized.

For this to work, add the text you want shown to your config/locale/en.yml (by default):

en:
  posts:
    create:
      flash:
        created: "Your post will now be reviewed before publishing"

  flash:
    created: "Successfully created"
    updated: "Successfully updated"

Here the posts#create action has a custom flash for the :created flash-message. All other controllers and actions in the application where a flash-message of :created is used the default message of "Successfully created" will be shown.

Next, add this to your ApplicationController (this is all of the magic):

  protected
  def flash_message cause, args = {}
    primary_key = "#{controller_name}.#{action_name}.flash.#{cause}"
    default_key = "flash.#{cause}".to_sym
    I18n.t primary_key, args.merge(default: default_key)
  end

Finally, this is how you use it within an action:

  flash[:notice] = flash_message(:created)
  # and
  redirect_to :root, notice: flash_message(:created)

Try to keep the actions somewhat generic like :created, :deleted, :updated, etc. This makes the default values easier to manage.

What just happened?

The I18n system has some neat convenience shortcuts we’re using here. First of all we build the primary flash lookup-key based on the current controller and action.

Second bit of functionality used here is the fallback message. Fallback messages can be given as an explicit string, or a symbol. When a symbol is used it will be used to lookup a new message in the I18n backend. We use that for the :default argument where the fallback is set to be a global flash message like flash.created.

Now you can customize all the flashes in your app without touching the code, you have all these small bits of user interface in a single file for easy overview. You can also easily vary the messages between languages, customize text where it is necessary, and have a convenient global fallback message.