Creating multiple nested forms using simple_form and rails 4

Question

I'm trying to create a simple app with the following models: categories --[has_many]--> questions --[has_many]--> answers

I have the following code for creating categories + questions(categories/_form.haml.html):

= simple_form_for(@category) do |f|
  = f.error_notification
  = f.input :title, label: "Category title: "
  = f.simple_fields_for :questions, @category.questions.build do |q|
    = q.input :content, label: "Question content: "
  = f.button :submit

And I'm using all the same code for creating questions + answers(questions/_form.haml.html). I have all the relations, strong parameters, nested attrs and controllers configured, it works just fine for me.

Two questions:

1. How to create multiple questions in categories/_form.haml.html?

2. How to create category + multiple questions + multiple answers per each question at once(in categories/_form.haml.html)?

I've spent a few hours trying to figure out how to accomplish the second one and all the info I was able to find is related to Rails 3.0 and form_for. None of them worked for me.

The most straightforward solution here should be something like:

= simple_form_for(@category) do |f|
  = f.error_notification
  = f.input :title, label: "Category title: "
  = f.simple_fields_for :questions, @category.questions.build do |q|
    = q.input :content, label: "Question content: "
    = q.simple_fields_for :answers, q.questions.build do |a|
      = a.input :content, label: "Answer content"
  = f.button :submit

But it gives me

undefined method `questions' for #<SimpleForm::FormBuilder:

What am I missing here?

Answer 1

You got it wrong here: = q.simple_fields_for :answers, q.questions.build do |a| You are calling questions method on builder object q instead of a model object. Probably You want this:

= q.simple_fields_for :answers, q.object.questions.build

Answer 2

i am not going to answer the first two questions as i think they are explained here in depth: http://railscasts.com/episodes/196-nested-model-form-part-1

i just want to give you some hints about the error. you really have to learn how to read error-messages and stacktraces if you want to become a professional.

so here is a detailed explanation of the error that states undefined methodquestions' for #

first of all, it is very important to provide complete stacktraces. that is because they include line numbers. line number are important when resolving issues.

i guess that the line in question here is = q.simple_fields_for :answers, q.questions.build do |a|

if you look at the message, it says that the object q is of type FormBuilder. this is the object that rails instantiates when you call form_for or fields_for. when you use SimpleForm, it's also in simple_form_for and simple_fields_for, but an extended version (most often called a decorated version).

this object q does not have a method question and never will! i assume that you want to access the underlying object that the fields_for method wraps. you can access this via q.object (see this post for more infos Rails - Using form_for and fields_for, how do you access the sub-object while in the fields_for block?).

in your case i also assume a mix of answers versus questions. i think that this should be q.simple_fields_for :answers, q.object.answers.build instead of q.simple_fields_for :answers, q.questions.build.