Should I prevent making I18n translation calls in models

Question

This is a question merely about code style.

I am working on a multilingual app in Ruby on Rails 4. My personal feeling tells me ideally to not do calls to I18n.t() in models, I just think model methods should be consistent, and not depending on varying environmental situations like the current user's locale, especially since I18n is usually related to views. I've got a few questions about this though:

1. Do you think this is a good rule in general?
2. How should I manage error messages in custom validation methods? Should I make exceptions for that scenario?
3. How should I manage customised keys that we use in form fields, such as the displayed text of a collection_select, that are partially translated? Is there a way to use view helpers for these occasions, that is (almost) as convenient as building model methods for these?

Answer 1

1. Yes. Translations belong to the view layer and only to the "display" part of it (that is, not to the API, which is still view)
2. Error messsages should be standard enough so you get to translate them correctly by iterating them in the view and getting the piecewise translations. Unfortunately that's not always possible because of different grammatical order of the sentences in languages. Still it's not useful to move those translations to the model. ActiveRecord's Errors class has hooks for translations just like ActiveModel, so the view can rely on them without injecting any i18n in the model itself.
3. Select helpers can often take a lambda as a label generator, you can use and abuse view paths and relative i18n keys and whatever you need without having to inject anything in the model. In case of doubt, use a presenter and inject I18n in it.