add limit of post per day

app/models/post.rb

@@ -5,6 +5,8 @@ class Post < ApplicationRecord
   validates :content, length: { maximum: 777 }
   validates :content, presence: true, if: :quoted_post?
 
+  validate :user, :limit_of_post_per_day
+
   def kind
     if quoted_post?
       :quoted_post
@@ -24,4 +26,12 @@ class Post < ApplicationRecord
   def repost?
     content.blank? && quoted_post_id
   end
+
+  def limit_of_post_per_day
+    posts_from_day = user.posts.where('created_at >= ?', Time.zone.now.beginning_of_day)
+
+    if posts_from_day.count >= 5
+      errors.add(:base, 'You can post only 5 posts per day')
+    end
+  end
 end

app/models/user.rb

@@ -7,4 +7,6 @@ class User < ApplicationRecord
             format: {
               with: /\A[a-zA-Z0-9]+\z/,
             }
+
+  has_many :posts
 end

app/models/user_follow.rb

@@ -7,6 +7,8 @@ class UserFollow < ApplicationRecord
   private
 
   def user_cant_follow_himself
-    errors.add(:followed, 'can\'t follow himself') if follower_id == followed_id
+    if follower_id == followed_id
+      errors.add(:followed, 'can\'t follow himself')
+    end
   end
 end

spec/models/post_spec.rb

@@ -28,4 +28,30 @@ RSpec.describe Post, type: :model do
       end
     end
   end
+
+  describe '#limit_of_post_per_day' do
+    context 'when user tries to post more than 5 times in a day' do
+      it 'returns error' do
+        user = create(:user)
+
+        5.times do
+          create(:post, user: user)
+        end
+
+        expect(build(:post, user: user).valid?).to be_falsey
+      end
+    end
+
+    context 'when the user has not yet reached their publication limit' do
+      it 'does not returns error' do
+        user = create(:user)
+
+        4.times do
+          create(:post, user: user)
+        end
+
+        expect(build(:post, user: user).valid?).to be_truthy
+      end
+    end
+  end
 end