Ajax answer update works

_answer.html.slim

- if answer.persisted?
  div class="answer-#{answer.id}"
    = answer.body
    - if current_user&.author_of? answer
      p= link_to 'Edit', '', class: 'edit-answer-link', data: { answer_id: answer.id }
      p= link_to "delete answer", answer_path(answer), method: :delete
      p
      = form_for [answer], remote: true, html: { id: "edit-answer-#{answer.id}"} do |f|
        = f.label :body, "Answer"
        = f.text_area :body
        = f.submit 'Save'

_answers.html.slim

- @question.answers.each do |answer|
  div class="answer-#{answer.id}"
    - if answer.persisted?
      p= answer.body
      - if current_user&.author_of? answer
        p= link_to 'Edit', '', class: 'edit-answer-link', data: { answer_id: answer.id }
        p= link_to "delete answer", answer_path(answer), method: :delete
        p
        = form_for [answer], remote: true, html: { id: "edit-answer-#{answer.id}"} do |f|
          = f.label :body, "Answer"
          = f.text_area :body
          = f.submit 'Save'

answers.coffee

# Place all the behaviors and hooks related to the matching controller here.
# All this logic will automatically be available in application.js.
# You can use CoffeeScript in this file: http://coffeescript.org/

# Объявляем функцию ready, внутри которой можно поместить обработчики событий и другой код,
# который должен выполняться при загрузке страницы

ready = ->
  $('.answers').on 'click', '.edit-answer-link', (e) ->
    e.preventDefault();
    $(this).hide();
    answer_id = $(this).data('answerId'); # answerId берется из дива
    $('form#edit-form').hide();
    $('form#edit-answer-' + answer_id).show();

$(document).ready(ready);                   # вешаем функцию ready на событие document.ready
$(document).on('turbolinks:load', ready);   # вешаем функцию ready на событие page:load
$(document).on('turbolinks:update', ready); # вешаем функцию ready на событие page:update

answers_controller.rb

class AnswersController < ApplicationController
  before_action :authenticate_user!
  before_action :load_question, only: [:create]
  before_action :load_answer, only: [:edit, :update, :destroy]

  def edit
  end

  def update
    if current_user&.author_of? @answer
    #if current_user.id == @answer.user_id
    @answer.update(answer_params)
    @question = @answer.question
    end
  end

  def create
    @answer = @question.answers.new(answer_params)
    @answer.user = current_user
    @answer.save
  end

  def destroy
    @question = @answer.question
    if current_user.author_of? @answer
      @answer.destroy!
      flash[:notice] = 'Your answer was successfully deleted.'
      redirect_to question_path(@question)
    else
      redirect_to question_path(@question)
    end
  end

  private

  def load_question
    @question = Question.find(params[:question_id])
  end

  def load_answer
    @answer = Answer.find(params[:id])
  end

  def answer_params
    params.require(:answer).permit(:body)
  end

end

create.js.erb

$('.answers').append('<%= j render @answer %>');
$('form#new_answer #answer_body').val('');
$('.errors').html("<%= j render 'shared/errors', object: @answer %>");

show.html.slim

h1 = @question.title
p = @question.body

- if current_user&.author_of? @question
  = link_to "delete question", question_path(@question), method: :delete

h2 Answers
.answers
   = render 'answers/answers'
 
- if user_signed_in?
  .errors
= render 'answers/form'

update.js.erb

<% if @answer.errors.present? %>
    <% @answer.errors.full_messages.each do |message| %>
        $('.errors').html('<%= j message %>');
    <% end %>
<% else %>
  $('#answer<%= @answer.id %>').replaceWith('<%= j render @answer %>');
  $('.answers').html("<%= j render 'answers' %>");
  $('.edit-answer-link').click(function(e) {
    e.preventDefault();
    $(this).hide();
    answer_id = $(this).data('answerId');
    $('form#edit-answer-' + answer_id).show();
});
<% end %>