Add description as comment on topic.

app/controllers/topics_controller.rb

@@ -44,7 +44,7 @@ class TopicsController < ApplicationController
   private
 
   def topic_params
-    params.require(:topic).permit(:title, :community_id)
+    params.require(:topic).permit(:title, :community_id, :description_as_comment)
   end
 
   def set_community

app/models/topic.rb

@@ -6,4 +6,12 @@ class Topic < ActiveRecord::Base
   belongs_to :author, -> { with_hidden }, class_name: 'User', foreign_key: 'author_id'
 
   has_many :comments, as: :commentable
+
+  after_create :associate_comment
+
+  private
+
+  def associate_comment
+    Comment.create(commentable: self, user: self.author, body: self.description_as_comment)
+  end
 end

app/views/topics/_form.html.erb

@@ -6,6 +6,8 @@
     <div class="small-12 column">
       <%= f.label :title, t("topic.form.topic_title") %>
       <%= f.text_field :title %>
+      <%= f.label :description_as_comment, t("topic.form.topic_description_as_comment") %>
+      <%= f.text_area :description_as_comment, maxlength: Comment.body_max_length %>
     </div>
 
     <div class="actions small-12 column">

db/migrate/20170807082243_create_topics.rb

@@ -2,6 +2,7 @@ class CreateTopics < ActiveRecord::Migration
   def change
     create_table :topics do |t|
       t.string :title, null: false
+      t.text   :description_as_comment
       t.integer :author_id
       t.integer  "comments_count", default: 0
       t.references :community, index: true

db/schema.rb

@@ -892,6 +892,7 @@ ActiveRecord::Schema.define(version: 20170807082243) do
 
   create_table "topics", force: :cascade do |t|
     t.string   "title",                              null: false
+    t.text     "description_as_comment"
     t.integer  "author_id"
     t.integer  "comments_count",         default: 0
     t.integer  "community_id"