notes.txt

# app/views/posts/show.html.erb

<br><br>
<h2>Comments</h2>
<div id="comments">
  <%# render partial: 'comments/comment', collection: @posts.comments %>
  <%= render @post.comments %>
</div>
  
<%= render 'comments/new', post: @post %>

# app/views/comments/_comment.html.erb
<p><%= comment.body %> -- <%= comment.created_at.to_s(:long) %></p>

# app/views/comments/_new.html.erb
<%= form_for([@post, Comment.new], remote: true) do |form| %>
  Your Comment:<br>
  <%= form.text_area :body, size: '50x20' %><br>
  <%= form.submit %>
<% end %>

# app/controllers/comments_controller.rb

class CommentsController < ApplicationController
  before_action :set_post
  
  def create
    @post.comments.create! comments_params
	redirect_to @post
  end
  
  private
  
  def set_post
    @post = Post.find(params[:post_id])
  end
  
  def comments_params
    params.required(:comment).permit(:body)
  end
end

# mailer
rails g mailer comments submitted

# app/mailers/comments_mailer.rb
class CommentsMailer < ApplicationMailer

  # Subject can be set in your I18n file at config/locales/en.yml
  # with the following lookup:
  #
  #   en.comments_mailer.submitted.subject
  #
  def submitted(comment)
    @comment = comment

    mail to: "blog-owner@example.org", subject: 'New Comment'
  end
end

# app/views/comments_mailers/submitted.html.erb

<h1>You got a new comment on <%= @comment.post.title %></h1>

<%= render @comment %>

# app/views/comments_mailers/submitted.text.erb
You got a new comment on <%= @comment.post.title %>: <%= @comment.body %>

# test/mailers/previews/comments_mailer_preview.rb

# Preview all emails at http://localhost:3000/rails/mailers/comments_mailer
class CommentsMailerPreview < ActionMailer::Preview

  # Preview this email at http://localhost:3000/rails/mailers/comments_mailer/submitted
  def submitted
    CommentsMailer.submitted Comment.first
  end

end

https://pos-univem-gabrielpedepera.c9users.io/rails/mailers/comments_mailer/submitted.html

# app/controllers/comments_controller.rb

comment = @post.comments.create! comments_params
CommentsMailer.submitted(comment).deliver_later

# Channel
rails g channel comments

# app/channels/comments_channel.rb (server_side)

# Be sure to restart your server when you modify this file. Action Cable runs in a loop that does not support auto reloading.
class CommentsChannel < ApplicationCable::Channel
  
  def self.broadcast(comment)
    broadcast_to comment.post, comment: 
      CommentsController.render(partial: 'comments/comment', locals: { comment: comment })
  end
  
  def subscribed
    stream_for Post.last
  end

  def unsubscribed
    # Any cleanup needed when channel is unsubscribed
  end
end

# app/assets/javascripts/channels/comments.coffee

App.comments = App.cable.subscriptions.create "CommentsChannel",
  connected: ->
    # Called when the subscription is ready for use on the server

  disconnected: ->
    # Called when the subscription has been terminated by the server

  received: (data) ->
    $('#comments').append data.comment

# app/controllers/comments_controller.rb

CommentsChannel.broadcast(comment)

# config.ru
ActionCable.server.config.disable_request_forgery_protection = true