Add attribute Post#published_at

app/models/post.rb

@@ -1,5 +1,7 @@
 class Post < ApplicationRecord
   belongs_to :profile
 
-  validates :text, length: { maximum: 200 }
+  validates :text, presence: true, length: { maximum: 200 }
+
+  validates :published_at, presence: true
 end

app/views/profiles/show.html.erb

@@ -11,7 +11,7 @@
 
       <p class="card-text">
         <small class="text-muted">
-          <%= localize post.created_at, format: :short %>
+          <%= localize post.published_at, format: :short %>
         </small>
       </p>
     </div>

db/migrate/20210310092955_create_posts.rb

@@ -4,6 +4,7 @@ class CreatePosts < ActiveRecord::Migration[6.1]
       t.timestamps
       t.references :profile, null: false, foreign_key: true
       t.string :text, null: false
+      t.datetime :published_at, null: false
     end
   end
 end

db/schema.rb

@@ -17,6 +17,7 @@ ActiveRecord::Schema.define(version: 2021_03_10_092955) do
     t.datetime "updated_at", precision: 6, null: false
     t.integer "profile_id", null: false
     t.string "text", null: false
+    t.datetime "published_at", null: false
     t.index ["profile_id"], name: "index_posts_on_profile_id"
   end