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rails new user_login

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# Use ActiveModel has_secure_password

gem 'bcrypt', '~> 3.1.7'

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rails g model user name:string password_digest:string

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# app/models/user.rb

class User < ActiveRecord::Base

 has_secure_password

end

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rake db:migrate

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rails g controller applicants new create

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post 'applicants/create'

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# app/controllers/applicants_controller.rb

class ApplicantsController < ApplicationController

 def new

  @user = User.new

 end

 def create

  @user = User.create(user_params)

  if @user.save

   redirect_to :sessions_new

  else

   render "new"

  end

 end

 private

  def user_params

   params.require(:user).permit(:name, :password, :password_confirmation)

  end

end

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<!-- app/views/applicants/new.html.erb -->

<h1>注册</h1>

<% if @user.errors.any? %>

<ul>

  <% @user.errors.full_messages.each do |message| %>

  <li><%= message %></li>

  <% end %>

</ul>

<% end %>

<%= form_for @user, url: :applicants_create do |f| %>

  <p>

    <%= f.label :name %>

    <%= f.text_field :name %>

  </p>

  <p>

    <%= f.label :password %>

    <%= f.password_field :password %>

  </p>

  <p>

    <%= f.label :password_confirmation %>

    <%= f.password_field :password_confirmation %>

  </p>

  <p><%= f.button "提交" %></p>

<% end %>

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rails g controller sessions new create

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# config/routes.rb

post 'sessions/create'

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# app/controllers/sessions_controller.rb

class SessionsController < ApplicationController

 def new

 end

 def create

  user = User.find_by(name: user_params[:name]).try(:authenticate, user_params[:password])

  if user

   render plain: sprintf("welcome, %s!", user.name)

  else

   flash.now[:login_error] = "invalid username or password"

   render "new"

  end

 end

 private

  def user_params

   params.require(:session).permit(:name, :password)

  end

end

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<!-- app/views/sessions/new.html.erb -->

<h1>登录</h1>

<% if flash[:login_error] %>

  <p><%= flash[:login_error] %></p>

<% end %>

<%= form_for :session, url: :sessions_create do |f| %>

  <p>

    <%= f.label :name %>

    <%= f.text_field :name %>

  </p>

  <p>

    <%= f.label :password %>

    <%= f.password_field :password %>

  </p>

  <p><%= f.button "登录" %></p>

<% end %>