panel/app/controllers/posts_controller.rb

class PostsController < ApplicationController
  before_action :authenticate!

  def index
    @site = find_site
  end

  def show
    @site = find_site
    @post = find_post(@site)
  end

  def edit
    @site = find_site
    @post = find_post(@site)
  end

  def update
    p = post_params
    @site = find_site
    @post = find_post(@site)

    # crear un array a partir de una cadena separada por comas
    [:tags,:categories].each do |comma|
      p[comma] = p.dig(comma).split(',').map(&:strip)
    end

    @post.update_attributes(p)
    if @post.save
      redirect_to site_post_path(@site, @post)
    else
      render 'posts/edit'
    end
  end

  private

  # Solo permitir cambiar estos atributos de cada articulo
  def post_params
    params.require(:post).permit(:title, :date, :tags,
      :categories, :content, :slug)
  end
end