Make a Relationship model

app/models/relationship.rb

@@ -0,0 +1,6 @@
+class Relationship < ActiveRecord::Base
+  belongs_to :follower, class_name: "User"
+  belongs_to :followed, class_name: "User"
+  validates :follower_id, presence: true
+  validates :followed_id, presence: true
+end

app/models/user.rb

@@ -2,11 +2,29 @@ class User < ActiveRecord::Base
   # Include default devise modules. Others available are:
   # :confirmable, :lockable, :timeoutable and :omniauthable
   has_many :microposts, dependent: :destroy
+  has_many :relationships, foreign_key: "follower_id", dependent: :destroy
+  has_many :followed_users, through: :relationships, source: :followed
+  has_many :reverse_relationships, foreign_key: "followed_id",
+                                   class_name:  "Relationship",
+                                   dependent:   :destroy
+  has_many :followers, through: :reverse_relationships, source: :follower
 
   def feed
     Micropost.where("user_id = ?", id)
   end
 
+  def following?(other_user)
+    relationships.find_by(followed_id: other_user.id)
+  end
+
+  def follow!(other_user)
+    relationships.create!(followed_id: other_user.id)
+  end
+
+  def unfollow!(other_user)
+    relationships.find_by(followed_id: other_user.id).destroy
+  end
+
   devise :database_authenticatable, :registerable,
          :recoverable, :rememberable, :trackable, :validatable
 

db/migrate/20180306140953_create_relationships.rb

@@ -0,0 +1,13 @@
+class CreateRelationships < ActiveRecord::Migration
+  def change
+    create_table :relationships do |t|
+      t.integer :follower_id
+      t.integer :followed_id
+
+      t.timestamps
+    end
+    add_index :relationships, :follower_id
+    add_index :relationships, :followed_id
+    add_index :relationships, [:follower_id, :followed_id], unique: true
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20180305154033) do
+ActiveRecord::Schema.define(version: 20180306140953) do
 
   create_table "microposts", force: true do |t|
     t.string   "content"
@@ -22,6 +22,17 @@
 
   add_index "microposts", ["user_id", "created_at"], name: "index_microposts_on_user_id_and_created_at"
 
+  create_table "relationships", force: true do |t|
+    t.integer  "follower_id"
+    t.integer  "followed_id"
+    t.datetime "created_at"
+    t.datetime "updated_at"
+  end
+
+  add_index "relationships", ["followed_id"], name: "index_relationships_on_followed_id"
+  add_index "relationships", ["follower_id", "followed_id"], name: "index_relationships_on_follower_id_and_followed_id", unique: true
+  add_index "relationships", ["follower_id"], name: "index_relationships_on_follower_id"
+
   create_table "users", force: true do |t|
     t.string   "name",                   default: "",    null: false
     t.string   "email",                  default: "",    null: false

test/fixtures/relationships.yml

@@ -0,0 +1,9 @@
+# Read about fixtures at http://api.rubyonrails.org/classes/ActiveRecord/FixtureSet.html
+
+one:
+  follower_id: 1
+  followed_id: 1
+
+two:
+  follower_id: 1
+  followed_id: 1

test/models/relationship_test.rb

@@ -0,0 +1,7 @@
+require 'test_helper'
+
+class RelationshipTest < ActiveSupport::TestCase
+  # test "the truth" do
+  #   assert true
+  # end
+end