Rails4: Formtastic3.0 , save multiple instances (for Answer models) at the same time

Question

I have Question model and an answer model.

Each question can have one answer per user. I am trying to preset to a user a form to answer all questions, but couldnt reall

Answer 1

Rather then making a form for @questions you need to pass a single object to your form helper (@questions is an array of questions). A good way to achieve this is though a form object.

# app/forms/questions_form.rb
class QuestionsForm
  include ActiveModel::Model

  def initialize(user)
    @user = user
  end

  def questions
    @questions ||= Question.all
  end

  def submit(params)
    params.questions.each_pair do |question_id, answer|
      answer = Answer.find_or_initialize_by(question_id: question_id, user: current_user)
      answer.content = answer
      answer.save
    end
  end

  def answer_for(question)
    answer = answers.select { |answer| answer.question_id == question.id }
    answer.try(:content)
  end

  def answers
    @answers ||= @user.answers.where(question: questions)
  end
end

Then in your controller you'd have:

# app/controllers/submissions_controller.rb
Class SubmissionsController < ApplicationController
  ...
  def new
    @questions_form = QuestionsForm.new(current_user)
  end

  def create
    @questions_form = QuestionsForm.new(current_user)

    @questions_form.submit(params[:questions_form])
    redirect_to # where-ever
  end
  ...
end

In your view you'll want something along the lines of:

# app/views/submissions/new.html.haml
= form_for @questions_form, url: submissions_path do |f|
  - @questions_form.questions.each do |question|
    %p= question.content
    = f.text_field "questions[#{question.id}]", value: @questions_form.answer_for(question)
  = f.submit "Submit"

This doesn't use formtastic at all, it's just using the plain rails form helpers.

This code isn't tested so not sure if it even works but hopefully it helps get you on the right track.