improve relations and scopes

app/models/post.rb

@@ -7,6 +7,10 @@ class Post < ApplicationRecord
 
   validate :user, :limit_of_post_per_day
 
+  scope :by_user_follows, ->(user) {
+    where(user_id: user.following_ids)
+  }
+
   def repost?
     kind == :quoted_post
   end

app/models/user.rb

@@ -9,4 +9,9 @@ class User < ApplicationRecord
             }
 
   has_many :posts
+
+  has_many :user_follows_following, class_name: 'UserFollow', foreign_key: :follower_id
+  has_many :user_follows_followers, class_name: 'UserFollow', foreign_key: :followed_id
+  has_many :following, through: :user_follows_following, source: :followed
+  has_many :followers, through: :user_follows_followers, source: :follower
 end

spec/models/post_spec.rb

@@ -1,6 +1,31 @@
 require 'rails_helper'
 
 RSpec.describe Post, type: :model do
+  describe 'scopes' do
+    context '#by_user_follows' do
+      it 'returns only posts from user follows ' do
+        followed_user = create(:user)
+        not_followed_user = create(:user)
+
+        post1 = create(:post, user: followed_user)
+        post2 = create(:post, user: followed_user)
+        create(:post, user: not_followed_user)
+
+        following_user = create(:user)
+        create(
+          :user_follow,
+          follower_id: following_user.id,
+          followed_id: followed_user.id
+        )
+
+        expect(Post.by_user_follows(following_user)).to eq([
+          post1,
+          post2
+        ])
+      end
+    end
+  end
+
   describe '#kind' do
     context 'when post have other post reference and a content' do
       it 'returns :quoted_post' do

spec/models/user_spec.rb

@@ -33,4 +33,32 @@ RSpec.describe User, type: :model do
       end
     end
   end
+
+  context '#relations' do
+    context 'following' do
+      it do
+        user1 = create(:user)
+        user2 = create(:user)
+        user3 = create(:user)
+
+        create(:user_follow, follower_id: user1.id, followed_id: user2.id)
+        create(:user_follow, follower_id: user3.id, followed_id: user1.id)
+
+        expect(user1.following).to eq([user2])
+      end
+    end
+
+    context 'followers' do
+      it do
+        user1 = create(:user)
+        user2 = create(:user)
+        user3 = create(:user)
+
+        create(:user_follow, follower_id: user1.id, followed_id: user2.id)
+        create(:user_follow, follower_id: user3.id, followed_id: user1.id)
+
+        expect(user1.followers).to eq([user3])
+      end
+    end
+  end
 end