Showing fields with errors for nested forms in Rails 3.2 + SimpleForm

If you are using simple_form with bootstrap, this does work - you just need to set up a few items correctly:

1 - Use the simple_form bootstrap wrappers (from simple_form 2.0) - you can find them in the github repo under config/initializers/simple_form.rb (https://github.com/rafaelfranca/simple_form-bootstrap)

2 - For nested forms to display the errors, you must be sure you provide an object. f.simple_fields_for :nested_model won't work, you need to use f.simple_fields_for parent_model.nested_model or f.simple_fields_for :nested_model, parent_model.nested_model so that the form can get the necessary object.

If you still don't get anything, verify that the form is really getting the object you think it is, with errors, by outputting the errors data on your nested object: parent_model.nested_model.errors.full_messages.to_sentence

I have been using custom accessors instead of the _id fields, so that's why they weren't getting notified when they had errors. I finally resolved to use f.error :attr_name under each accessor and changing the styling manually with JS

There might be several things wrong along the way. I had issues with this as well using bootstrap simple form. After I fixed everything in the controller, model and form it worked.

For me I had several issues, especially the commented lines where crucial in my case.

check that you have the following in place:

survey.rb:

class Survey < ApplicationRecord  has_many :answers  accepts_nested_attributes_for :answers, allow_destroy: true  #errors have to come from answer validation for answer form  validates_associated :answers  validates :question, :answers, presence: true

answer.rb:

class Answer < ApplicationRecord  belongs_to :survey  # make sure there is a validation on answer  validates :answer, presence: trueend

_form.html.slim

# make sure you have given the right attributes for .input and simple_fields_for= f.simple_fields_for :answers, @survey.answers do |answer_form|  = answer_form.input :answer

surveys_controller.rb

def new @survey = Survey.new #when answers are not builded it wont show any simple fields for @survey.answers.buildenddef create @survey = Survey.new(survey_params) @survey.user = current_backend_user if @survey.save  redirect_to backend_surveys_path, notice: 'Umfrage erfolgreich erstellt' else  render :new endenddef survey_params  # make sure everything is permitted correctly  params.require(:survey).permit(:some_attribute, ..., answers_attributes: %i[id answer])end

reject if on model validation can cause errors some times on this as well. be cautious.