【Rails】bcryptを使ってログイン機能を実装する方法

# Use ActiveModel has_secure_password
gem 'bcrypt', '~> 3.1.7'

bundle install

bin/rails g migration AddUsers1

class AddUsers1 < ActiveRecord::Migration[5.2]
  def change
    add_column :users, :password_digest, :string
  end
end

bin/rails db:migrate

class User < ApplicationRecord
  has_secure_password
(以下略)

User.create!(省略, password:"パスワード", password_confirmation:"パスワード")

resource :login ,only: [:create, :destroy]

bin/rails g controller logins

class LoginsController < ApplicationController
  def create #ログイン
    user=User.find_by(login_id:params[:login_id])
    if user && user&.authenticate(params[:password])
      session[:user_id]=user.id
      flash.alert="ログインに成功しました" 
    else
      flash.alert="ログインに失敗しました"
      redirect_to("/")
    end
  end

  def destroy #ログアウト
    session.delete(:user_id)
    redirect_to("/")
  end
end

<%=form_tag :session,id:"login_form" do%>
  <div>
    <label>id:</label>
    <input type="text" name="login_id">
  </div>

  <div>
    <label>パスワード</label>
    <input type="text" name="password">
  </div>

  <div>
    <input type="submit" value="ログイン">
  </div>
<%end%>

class ApplicationController < ActionController::Base
  private def current_user
    if session[:user_id]
      User.find_by(id:session[:user_id])
    end
  end
(省略)

<%if current_user%>
  <%="#{current_user.name}さん"%>
  <%=link_to("ログアウト",:login,method: :delete,data:{confirm:"本当にログアウトしますか?"})%>
<%end%>

irb(main):001:0> User.all
You don't have bcrypt installed in your application. Please add it to your Gemfile and run bundle install
Traceback (most recent call last):
        3: from (irb):1
        2: from app/models/user.rb:1:in `<main>'
        1: from app/models/user.rb:2:in `<class:User>'
LoadError (cannot load such file -- bcrypt)