Show full error messages with simple form?

Question

How do I output the full error message of a field using simple form? The equivalent of rails: <%= RESOURCE.errors.full_messages %>

e.g. show this:

Answer 1

If anyone is still wondering there is an easy way to do this now, as referenced here

Simply under config/initializers/simple_form.rb change b.user :error to b.user :full_error and now your error messages will be the equivalent of RESOURCE.errors.full_messages

Note: if you are using bootstrap w/ simple form you change simple_form_bootstrap.rb