✨ create Follow model

app/models/follow.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+class Follow < ApplicationRecord
+  belongs_to :follower, class_name: "User", inverse_of: :follower_follows
+  belongs_to :followed, class_name: "User", inverse_of: :followed_follows
+
+  validates :follower, uniqueness: { scope: :followed_id }
+
+  validate :follower_and_followed_cannot_be_the_same
+
+  private
+
+  def follower_and_followed_cannot_be_the_same
+    return unless follower_id == followed_id
+
+    errors.add(:base, :follower_and_followed_cannot_be_the_same)
+  end
+end

app/models/user.rb

@@ -8,6 +8,12 @@ class User < ApplicationRecord
 
   has_one :profile, class_name: "UserProfile", dependent: :destroy
 
+  has_many :follower_follows, class_name: "Follow", inverse_of: :follower, dependent: :destroy,
+    foreign_key: "follower_id"
+  has_many :following, through: :follower_follows, source: :followed
+  has_many :followed_follows, class_name: "Follow", inverse_of: :followed, dependent: :destroy,
+    foreign_key: "followed_id"
+  has_many :followers, through: :followed_follows, source: :follower
   has_many :likes, dependent: :destroy
   has_many :posts, dependent: :destroy
 

config/locales/pt-BR/models/core.yml

@@ -1,12 +1,17 @@
 pt-BR:
   activerecord:
     models:
+      follow: Seguir
       like: Curtida
       post: Publicação
       user_profile: Perfil
       user: Usuário
 
     attributes:
+      follow:
+        follower: Seguidor
+        followed: Seguido
+
       like:
         post: Publicação
         user: Usuário
@@ -26,3 +31,8 @@ pt-BR:
       user:
         email: E-mail
         password: Senha
+
+    errors:
+      models:
+        follow:
+          follower_and_followed_cannot_be_the_same: Não é possível seguir a si mesmo

db/migrate/20240706163329_create_follows.rb

@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+class CreateFollows < ActiveRecord::Migration[7.0]
+  def change
+    create_table :follows, id: :uuid do |t|
+      t.references :follower, null: false, foreign_key: { to_table: :users }, type: :uuid
+      t.references :followed, null: false, foreign_key: { to_table: :users }, type: :uuid
+
+      t.timestamps
+    end
+
+    add_index :follows, %i[follower_id followed_id], unique: true
+  end
+end

spec/factories/follows_factories.rb

@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+FactoryBot.define do
+  factory :follow do
+    association :follower, factory: :user, strategy: :create
+    association :followed, factory: :user, strategy: :create
+  end
+end

spec/models/follow_spec.rb

@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+require "rails_helper"
+
+RSpec.describe Follow do
+  describe "associations" do
+    it { is_expected.to belong_to(:follower).class_name("User").inverse_of(:follower_follows) }
+    it { is_expected.to belong_to(:followed).class_name("User").inverse_of(:followed_follows) }
+  end
+
+  describe "validations" do
+    it "validates uniqueness of the pair follower_id and followed_id" do
+      follow = create(:follow)
+
+      expect(follow).to validate_uniqueness_of(:follower).scoped_to(:followed_id)
+    end
+
+    context "when follower and followed are the same" do
+      it "adds an error message to :base" do
+        user = create(:user)
+        follow = described_class.new(follower: user, followed: user)
+        follow.valid?
+
+        error_message = I18n.t("activerecord.errors.models.follow.follower_and_followed_cannot_be_the_same")
+
+        expect(follow.errors[:base]).to include(error_message)
+      end
+    end
+
+    context "when follower and followed aren't the same" do
+      it "doesn't add an error message to :base" do
+        follow = create(:follow)
+
+        error_message = I18n.t("activerecord.errors.models.follow.follower_and_followed_cannot_be_the_same")
+
+        expect(follow.errors[:base]).not_to include(error_message)
+      end
+    end
+  end
+end

spec/models/user_spec.rb

@@ -4,10 +4,23 @@
 
 RSpec.describe User do
   describe "associations" do
-    it { is_expected.to have_many(:likes) }
-
     it { is_expected.to have_one(:profile) }
 
+    it do
+      expect(described_class.new).to have_many(:follower_follows).class_name("Follow").inverse_of(:follower)
+        .dependent(:destroy).with_foreign_key("follower_id")
+    end
+
+    it do
+      expect(described_class.new).to have_many(:followed_follows).class_name("Follow").inverse_of(:followed)
+      .dependent(:destroy).with_foreign_key("followed_id")
+    end
+
+    it { is_expected.to have_many(:following).through(:follower_follows).source(:followed) }
+    it { is_expected.to have_many(:followers).through(:followed_follows).source(:follower) }
+    it { is_expected.to have_many(:likes) }
+    it { is_expected.to have_many(:posts) }
+
     it { is_expected.to accept_nested_attributes_for(:profile) }
   end