$ rails generate migration add_remember_digest_to_users remember_digest:string
$ rails db:migrate

$ rails console
>> SecureRandom.urlsafe_base64
=> "brl_446-8bqHv87AQzUj_Q"

defUser.new_tokenSecureRandom.urlsafe_base64end

defrememberself.remember_token=User.new_tokenupdate_attribute(:remember_digest,User.digest(remember_token))end

cookies.signed[:user_id]=user.id

cookies.permanent.signed[:user_id]=user.id

# 渡されたトークンがダイジェストと一致したらtrueを返すdefauthenticated?(remember_token)BCrypt::Password.new(remember_digest).is_password?(remember_token)end

defcreateuser=User.find_by(email: params[:session][:email].downcase)ifuser&&user.authenticate(params[:session][:password])log_inuserrememberuserredirect_touserelseflash.now[:danger]='Invalid email/password combination'render'new'endend

# ユーザーのセッションを永続的にするdefremember(user)user.remember#Userモデルのメソッド（記憶トークンの生成、ダイジェストトークンのDB保存）cookies.permanent.signed[:user_id]=user.idcookies.permanent[:remember_token]=user.remember_tokenend

# 記憶トークンcookieに対応するユーザーを返すdefcurrent_userif(user_id=session[:user_id])@current_user||=User.find_by(id: user_id)elsif(user_id=cookies.signed[:user_id])user=User.find_by(id: user_id)ifuser&&user.authenticated?(cookies[:remember_token])log_inuser@current_user=userendendend

FAIL["test_login_with_valid_information_followed_by_logout", #<Minitest::Reporters::Suite:0x0000556848d6b040 @name="UsersLoginTest">, 1.7997455329999923]
 test_login_with_valid_information_followed_by_logout#UsersLoginTest (1.80s)
        Expected at least 1 element matching "a[href="/login"]", found 0..
        Expected 0 to be >= 1.
        test/integration/users_login_test.rb:36:in `block in <class:UsersLoginTest>'

# ユーザーのログイン情報を破棄するdefforgetupdate_attribute(:remember_digest,nil)end

　defforget(user)user.forgetcookies.delete(:user_id)cookies.delete(:remember_token)end

　deflog_outforget(current_user)session.delete(:user_id)@current_user=nilend

NoMethodError: undefined method `forget' for nil:NilClass
app/helpers/sessions_helper.rb:36:in `forget'
app/helpers/sessions_helper.rb:24:in `log_out'
app/controllers/sessions_controller.rb:20:in `destroy'

require'test_helper'classUsersLoginTest<ActionDispatch::IntegrationTest...test"login with valid information followed by logout"dogetlogin_pathpostlogin_path,params: {session: {email:    @user.email,password: 'password'}}assertis_logged_in?assert_redirected_to@userfollow_redirect!assert_template'users/show'assert_select"a[href=?]",login_path,count: 0assert_select"a[href=?]",logout_pathassert_select"a[href=?]",user_path(@user)deletelogout_pathassert_notis_logged_in?assert_redirected_toroot_url# ↓ここで再度delete logout_pathをリクエストdeletelogout_pathfollow_redirect!assert_select"a[href=?]",login_pathassert_select"a[href=?]",logout_path,count: 0assert_select"a[href=?]",user_path(@user),count: 0endend

  def logged_in?
    !current_user.nil?
  end

defdestroylog_outiflogged_in?redirect_toroot_urlend

defcurrent_userif(user_id=session[:user_id])@current_user||=User.find_by(id: user_id)elsif(user_id=cookies.signed[:user_id])#ここでtrueになるuser=User.find_by(id: user_id)ifuser&&user.authenticated?(cookies[:remember_token])#エラーlog_inuser@current_user=userendendend

defauthenticated?(remember_token)BCrypt::Password.new(remember_digest).is_password?(remember_token)#remember_digest = nilend

BCrypt::Errors::InvalidHash: invalid hash

require'test_helper'classUserTest<ActiveSupport::TestCasedefsetup@user=User.new(name: "Example User",email: "user@example.com",password: "foobar",password_confirmation: "foobar")end...test"authenticated? should return false for a user with nil digest"doassert_not@user.authenticated?('')endend

defauthenticated?(remember_token)returnfalseifremember_digest.nil?BCrypt::Password.new(remember_digest).is_password?(remember_token)end

<%=f.label:remember_me,class:"checkboxinline"do%><%=f.check_box:remember_me%><span>Remember me on this computer</span><%end%>

.../*forms*/....checkbox{margin-top:-10px;margin-bottom:10px;span{margin-left:20px;font-weight:normal;}}#session_remember_me{width:auto;margin-left:0;}

ifparams[:session][:remember_me]=='1'remember(user)elseforget(user)end

params[:session][:remember_me]=='1'?remember(user):forget(user)

ENV['RAILS_ENV']||='test'...classActiveSupport::TestCasefixtures:all# テストユーザーがログイン中の場合にtrueを返すdefis_logged_in?!session[:user_id].nil?end# テストユーザーとしてログインするdeflog_in_as(user)session[:user_id]=user.idendendclassActionDispatch::IntegrationTest# テストユーザーとしてログインするdeflog_in_as(user,password: 'password',remember_me: '1')postlogin_path,params: {session: {email: user.email,password: password,remember_me: remember_me}}endend

defcreate@user=User.find_by(email: params[:session][:email].downcase)if@user&.authenticate(params[:session][:password])log_in@userparams[:session][:remember_me]=='1'?remember(@user):forget(@user)redirect_to@userelseflash.now[:danger]='Invalid email/password combination'render'new'endend

test"login with remembering"dolog_in_as(@user,remember_me: '1')assert_equalcookies[:remember_token],assigns(:user).remember_tokenend

require'test_helper'classSessionsHelperTest<ActionView::TestCasedefsetup@user=users(:michael)remember(@user)endtest"current_user returns right user when session is nil"doassert_equal@user,current_userassertis_logged_in?endtest"current_user returns nil when remember digest is wrong"do@user.update_attribute(:remember_digest,User.digest(User.new_token))assert_nilcurrent_userendend

$ heroku maintenance:on
$ git push heroku
$ heroku run rails db:migrate
$ heroku maintenance:off