Question

I have a collection with predefined questions and a user whom should answer all these questions. So the view should be something like:

= form_for @user do |f|
  -#some code and then...
    %table.table
      - @questions.each do |q|
        %tr
          %td=q.name
          %td
            %input-# Here the answer of the user for the question 'q'

So the view should show too each of the user answers for each question. My problem is that in first instance there shouldn’t be any answer, so I couldn’t use something like:

= form_for @user do |f|
  -#some code and then...
    %table.table
      - @user.answers.each do |answer|
        = f.fields_for :answers, answer do |a|
          %tr
            %td= answer.question.name
            %td=a.number_field :result

In this case there won’t be any answers so nothing will show. Even if there would be an answer I must to show all the questions to the user. I could just pre-initialize the answers with empty values, but I don’t want to have a bunch of records just with empty values(most of these questions maybe never will be answered by the user). Another thing is that the questions has an order and I don’t know how is gonna be sorted with the @user.answers.each loop (yeah, I could modify the query, so it could be sorted, but I would be tweaking too much for something…simple?). In general the main loop should be @questions.each and not @user.answers.each.

I’ve been thinking in some nasty ways to do that, like creating the fields manually, several if/else conditions, but I’m hoping that rails has a clean way to do that. Somebody has crossed with a problem like this before? There’s no other way to do that but create all of these with custom helpers?. Thanks in advance

Update

At the end, thanks to @saverio answer, I left it as follows:

%table.table
  - @questions.each_with_index do |q, i|
    %tr
      %td= q.name
      %td
        - answer = @user.answers.detect{|a| a.question.try(:id) == q.id}
        = number_field_tag "user[answers_attributes][#{i}][result]", (answer && answer.result)
        = hidden_field_tag "user[answers_attributes][#{i}][id]", (answer && answer.id)
        = hidden_field_tag "user[answers_attributes][#{i}][question_id]", q.id

In the controller, with the next line, was enough to clean all the empty values:

params[:user][:answers_attributes].delete_if{|k,v| v[:result].blank? && v[:id].blank?}

Answer 1

Loop over @questions, and at each step show a field for the corresponding answer. If an answer has been provided, show it as preloaded text

= form_for @user do |f|
  -#some code and then...
    %table.table
      - @questions.each do |q|
        - answer = @user.answers.detect {|a| a.question.name == q}
        %tr
          %td= q.name
          %td= text_field_tag "user[answers][#{q.id}]", (answer && answer.text)

In the controller you’ll have to parse the params[:user][:answers], which will be a hash from the question’s ID to the provided answer.