made the ajax

app/assets/stylesheets/custom.css.scss

@@ -149,6 +149,35 @@ aside {
   margin-right: 10px;
 }
 
+.stats {
+  overflow: auto;
+  a {
+    float: left;
+    padding: 0 10px;
+    border-left: 1px solid $gray-light;
+    color: gray;
+    &:first-child {
+      padding-left: 0;
+      border: 0;
+    }
+    &:hover {
+      text-decoration: none;
+      color: #4c61a8;
+    }
+  }
+  strong {
+    display: block;
+  }
+}
+
+.user_avatars {
+  overflow: auto;
+  margin-top: 10px;
+  .gravatar {
+    margin: 1px 1px;
+  }
+}
+
 /* forms */
 
 input, textarea, select, .uneditable-input {

app/controllers/relationships_controller.rb

@@ -0,0 +1,21 @@
+class RelationshipsController < ApplicationController
+  before_action :signed_in_user
+
+  def create
+    @user = User.find(params[:relationship][:followed_id])
+    current_user.follow!(@user)
+    respond_to do |format|
+      format.html { redirect_to @user }
+      format.js
+    end
+  end
+
+  def destroy
+    @user = Relationship.find(params[:id]).followed
+    current_user.unfollow!(@user)
+    respond_to do |format|
+      format.html { redirect_to @user }
+      format.js
+    end
+  end
+end

app/controllers/users_controller.rb

@@ -1,5 +1,6 @@
 class UsersController < ApplicationController
-  before_action :signed_in_user, only: [:index, :edit, :update, :destroy]
+  before_action :signed_in_user,
+	 only: [:index, :edit, :update, :destroy, :following, :followers]
   before_action :correct_user,   only: [:edit, :update]
   before_action :admin_user,     only: :destroy
   before_action :signined,       only: [:new, :create]
@@ -53,6 +54,20 @@ def destroy
     end
   end
 
+  def following
+    @title = "Following"
+    @user = User.find(params[:id])
+    @users = @user.followed_users.paginate(page: params[:page])
+    render 'show_follow'
+  end
+
+  def followers
+    @title = "Followers"
+    @user = User.find(params[:id])
+    @users = @user.followers.paginate(page: params[:page])
+    render 'show_follow'
+  end
+
   private
 
   def user_params

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

@@ -1,5 +1,7 @@
 class User < ActiveRecord::Base
   has_many :microposts, dependent: :destroy
+  has_many :relationships, foreign_key: "follower_id", dependent: :destroy
+  has_many :followed_users, through: :relationships, source: :followed
   before_save { self.email = email.downcase }
   before_create :create_remember_token
 
@@ -10,6 +12,11 @@ class User < ActiveRecord::Base
   has_secure_password
   validates :password, length: { minimum: 6 }
 
+  has_many :reverse_relationships, foreign_key: "followed_id",
+                                   class_name:  "Relationship",
+                                   dependent:   :destroy
+  has_many :followers, through: :reverse_relationships, source: :follower
+
   def User.new_remember_token
     SecureRandom.urlsafe_base64
   end
@@ -22,6 +29,18 @@ 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
+
   private
   def create_remember_token
     self.remember_token = User.encrypt(User.new_remember_token)

app/views/relationships/create.js.erb

@@ -0,0 +1,2 @@
+$("#follow_form").html("<%= escape_jaevscript(render('users/unfollow')) %>")
+$("#followers").html('<%= @user.followers/count %>')

app/views/relationships/destroy.js.erb

@@ -0,0 +1,2 @@
+$("#follow_form").html("<%= escape_jaevscript(render('users/unfollow')) %>")
+$("#followers").html('<%= @user.followers/count %>')

app/views/shared/_home_signed_in.html.erb

@@ -3,6 +3,9 @@
     <section>
       <%= render 'shared/user_info' %>
     </section>
+    <section>
+      <%= render 'shared/stats' %>
+    </section>
     <section>
       <%= render 'shared/micropost_form' %>
     </section>

app/views/shared/_stats.html.erb

@@ -0,0 +1,15 @@
+<% @user ||= current_user %>
+<div class="stats">
+  <a href="<%= following_user_path(@user) %>">
+    <strong id="following" class="stat">
+      <%= @user.followed_users.count %>
+    </strong>
+    following
+  </a>
+  <a href="<%= followers_user_path(@user) %>">
+    <strong id="followers" class="stat">
+      <%= @user.followers.count %>
+    </strong>
+    followers
+  </a>
+</div>

app/views/users/_follow.html.erb

@@ -0,0 +1,5 @@
+<%= form_for(current_user.relationships.build(followed_id: @user.id),
+        remote: true) do |f| %>
+  <div><%= f.hidden_field :followed_id %></div>
+  <%= f.submit "Follow", class: "btn btn-large btn-primary" %>
+<% end %>

app/views/users/_follow_form.html.erb

@@ -0,0 +1,9 @@
+<% unless current_user?(@user) %>
+  <div id="follow_form">
+  <% if current_user.following?(@user) %>
+    <%= render 'unfollow' %>
+  <% else %>
+    <%= render 'follow' %>
+  <% end %>
+  </div>
+<% end %>

app/views/users/_unfollow.html.erb

@@ -0,0 +1,4 @@
+<%= form_for(current_user.relationships.find_by(followed_id: @user.id),
+             html: { method: :delete }, remote: true) do |f| %>
+  <%= f.submit "Unfollow", class: "btn btn-large" %>
+<% end %>

app/views/users/show.html.erb

@@ -7,8 +7,12 @@
         <%= @user.name %>
       </h1>
     </section>
+    <section>
+      <%= render 'shared/stats' %>
+    </section>
   </aside>
   <div class="span8">
+    <%= render 'follow_form' if signed_in? %>
     <% if @user.microposts.any? %>
       <h3>Microposts (<%= @user.microposts.count %>)</h3>
       <ol class="microposts">

app/views/users/show_follow.html.erb

@@ -0,0 +1,30 @@
+<% provide(:title, @title) %>
+<div class="row">
+  <aside class="span4">
+    <section>
+      <%= gravatar_for @user %>
+      <h1><%= @user.name %></h1>
+      <span><%= link_to "view my profile", @user %></span>
+      <span><b>Microposts:</b> <%= @user.microposts.count %></span>
+    </section>
+    <section>
+      <%= render 'shared/stats' %>
+      <% if @users.any? %>
+        <div class="user_avatars">
+          <% @users.each do |user| %>
+            <%= link_to gravatar_for(user, size: 30), user %>
+          <% end %>
+        </div>
+      <% end %>
+    </section>
+  </aside>
+  <div class="span8">
+    <h3><%= @title %></h3>
+    <% if @users.any? %>
+      <ul class="users">
+        <%= render @users %>
+      </ul>
+      <%= will_paginate %>
+    <% end %>
+  </div>
+</div>

config/routes.rb

@@ -1,7 +1,12 @@
 Rails.application.routes.draw do
-  resources :users
+  resources :users do
+    member do
+      get :following, :followers
+    end
+  end
   resources :sessions, only: [:new, :create, :destroy]
   resources :microposts, only: [:create, :destroy]
+  resources :relationships, only: [:create, :destroy]
   root  'static_pages#home'
   match '/signup',  to: 'users#new',            via: 'get'
   match '/signin',  to: 'sessions#new',         via: 'get'

db/migrate/20151216140000_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 null: false
+    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: 20151211161025) do
+ActiveRecord::Schema.define(version: 20151216140000) do
 
   create_table "microposts", force: :cascade 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", using: :btree
 
+  create_table "relationships", force: :cascade do |t|
+    t.integer  "follower_id"
+    t.integer  "followed_id"
+    t.datetime "created_at",  null: false
+    t.datetime "updated_at",  null: false
+  end
+
+  add_index "relationships", ["followed_id"], name: "index_relationships_on_followed_id", using: :btree
+  add_index "relationships", ["follower_id", "followed_id"], name: "index_relationships_on_follower_id_and_followed_id", unique: true, using: :btree
+  add_index "relationships", ["follower_id"], name: "index_relationships_on_follower_id", using: :btree
+
   create_table "users", force: :cascade do |t|
     t.string   "name"
     t.string   "email"

lib/tasks/sample_data.rake

@@ -1,24 +1,42 @@
 namespace :db do
   desc "Fill database with sample data"
   task populate: :environment do
-    User.create!(name: "Example User",
-                 email: "example@railstutorial.jp",
-                 password: "foobar",
-                 password_confirmation: "foobar",
-                 admin: true)
-    99.times do |n|
-      name  = Faker::Name.name
-      email = "example-#{n+1}@railstutorial.jp"
-      password  = "password"
-      User.create!(name: name,
-                   email: email,
-                   password: password,
-                   password_confirmation: password)
-    end
-    users = User.all.limit(6)
-    50.times do
-      content = Faker::Lorem.sentence(5)
-      users.each { |user| user.microposts.create!(content: content) }
-    end
+    make_users
+    make_microposts
+    make_relationships
   end
 end
+
+def make_users
+  admin = User.create!(name:     "Example User",
+                       email:    "example@railstutorial.jp",
+                       password: "foobar",
+                       password_confirmation: "foobar",
+                       admin: true)
+  99.times do |n|
+    name  = Faker::Name.name
+    email = "example-#{n+1}@railstutorial.jp"
+    password  = "password"
+    User.create!(name:     name,
+                 email:    email,
+                 password: password,
+                 password_confirmation: password)
+  end
+end
+
+def make_microposts
+  users = User.all.limit(6)
+  50.times do
+    content = Faker::Lorem.sentence(5)
+    users.each { |user| user.microposts.create!(content: content) }
+  end
+end
+
+def make_relationships
+  users = User.all
+  user  = users.first
+  followed_users = users[2..50]
+  followers      = users[3..40]
+  followed_users.each { |followed| user.follow!(followed) }
+  followers.each      { |follower| follower.follow!(user) }
+end

spec/controllers/relationships_controller_spec.rb

@@ -0,0 +1,40 @@
+require 'rails_helper'
+
+RSpec.describe RelationshipsController do
+  let(:user) { FactoryGirl.create(:user) }
+  let(:other_user) { FactoryGirl.create(:user) }
+
+  before { sign_in user, no_capybara: true }
+
+  describe "creating a relationship with Ajac" do
+    it "should increment the Relationship count" do
+      expect do
+        xhr :post, :create, relationship: { followed_id: other_user.id }
+      end.to change(Relationship, :count).by(1)
+    end
+
+    it "should respond with cuccess" do
+      xhr :post, :create, relationship: { followed_id: other_user.id }
+      expect(response).to be_success
+    end
+  end
+
+  describe "destroying a relationship with Ajax" do
+    before { user.follow!(other_user) }
+
+    let(:relationship) do
+      user.relationships.find_by(followed_id: other_user.id)
+    end
+
+    it "should decrement the Relationship count" do
+      expect do
+        xhr :delete, :destroy, id: relationship.id
+      end.to change(Relationship, :count).by(-1)
+    end
+
+    it "shoud respond with success" do
+      xhr :delete, :destroy, id: relationship.id
+      expect(response).to be_success
+    end 
+  end
+end